diff --git a/config.h.in b/config.h.in
index 79bf3e9a2..1168b38db 100644
--- a/config.h.in
+++ b/config.h.in
@@ -258,6 +258,9 @@
 /* Define to 1 if you have the `faccessat' function. */
 #undef HAVE_FACCESSAT
 
+/* Define to 1 if the compiler supports the fallthrough attribute. */
+#undef HAVE_FALLTHROUGH_ATTRIBUTE
+
 /* Define to 1 if you have the `fchmodat' function. */
 #undef HAVE_FCHMODAT
 
@@ -1038,8 +1041,8 @@
 /* Define to 1 if you want sudo to free up memory before exiting. */
 #undef NO_LEAKS
 
-/* Define to 1 if you don't want users to get the lecture the first time they use
-   sudo. */
+/* Define to 1 if you don't want users to get the lecture the first time they
+   use sudo. */
 #undef NO_LECTURE
 
 /* Define to 1 if you don't want to use sudo's PAM session support. */
diff --git a/configure b/configure
index 2ef7f19a1..697d56f6a 100755
--- a/configure
+++ b/configure
@@ -27860,43 +27860,48 @@ _ACEOF
 
 if test -n "$GCC"; then
     if test X"$enable_warnings" = X"yes" -o X"$with_devel" = X"yes"; then
-	CFLAGS="${CFLAGS} -Wall -Wsign-compare -Wpointer-arith"
-						_CFLAGS="$CFLAGS"
-	CFLAGS="$CFLAGS -Wimplicit-fallthrough -Werror"
-	{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler acceptd -Wimplicit-fallthrough" >&5
-$as_echo_n "checking whether C compiler acceptd -Wimplicit-fallthrough... " >&6; }
-	cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+				CFLAGS="${CFLAGS} -Wall -Wsign-compare -Wpointer-arith"
+					{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports the fallthrough attribute" >&5
+$as_echo_n "checking whether $CC supports the fallthrough attribute... " >&6; }
+if ${sudo_cv_var_fallthrough_attribute+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
-	    int main(int argc, char *argv[])
-	    {
-		int num = argc + 1;
-		switch (num) {
-		    case 1:
-			num = 0;
-			/* FALLTHROUGH */
-		    case 0:
-			num++;
+		int main(int argc, char *argv[])
+		{
+		    int num = argc + 1;
+		    switch (num) {
+			case 1:
+			    num = 0;
+			    __attribute__((__fallthrough__));
+			case 0:
+			    num++;
+		    }
+		    return num;
 		}
-		return num;
-	    }
 
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
 
-	    { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
-$as_echo "yes" >&6; }
-	    CFLAGS="$_CFLAGS -Wimplicit-fallthrough"
+		sudo_cv_var_fallthrough_attribute=yes
 
 else
 
-	    { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-	    CFLAGS="$_CFLAGS"
+		sudo_cv_var_fallthrough_attribute=no
 
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $sudo_cv_var_fallthrough_attribute" >&5
+$as_echo "$sudo_cv_var_fallthrough_attribute" >&6; }
+	if test X"$sudo_cv_var_fallthrough_attribute" = X"yes"; then
+	    $as_echo "#define HAVE_FALLTHROUGH_ATTRIBUTE 1" >>confdefs.h
+
+	    CFLAGS="$CFLAGS -Wimplicit-fallthrough"
+	fi
     fi
     if test X"$enable_werror" = X"yes"; then
 	CFLAGS="${CFLAGS} -Werror"
@@ -30315,5 +30320,6 @@ fi
 
 
 
+
 
 
diff --git a/configure.ac b/configure.ac
index befc3271f..098b61b02 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4591,36 +4591,41 @@ dnl We add -Wall and -Werror after all tests so they don't cause failures
 dnl
 if test -n "$GCC"; then
     if test X"$enable_warnings" = X"yes" -o X"$with_devel" = X"yes"; then
+	dnl
+	dnl Default warnings for development use.
+	dnl
 	CFLAGS="${CFLAGS} -Wall -Wsign-compare -Wpointer-arith"
 	dnl
-	dnl Check whether -Wimplicit-fallthrough is available and
-	dnl recognizes /* FALLTHROUGH */ comments.  Clang 10 requires
-	dnl the "fallthrough" attribute which we don't use.
+	dnl The fallthrough attribute is supported by gcc 7.0 and clang 10.
+	dnl This test relies on AC_LANG_WERROR.
 	dnl
-	_CFLAGS="$CFLAGS"
-	CFLAGS="$CFLAGS -Wimplicit-fallthrough -Werror"
-	AC_MSG_CHECKING([whether C compiler acceptd -Wimplicit-fallthrough])
-	AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
-	    int main(int argc, char *argv[])
-	    {
-		int num = argc + 1;
-		switch (num) {
-		    case 1:
-			num = 0;
-			/* FALLTHROUGH */
-		    case 0:
-			num++;
+	AC_CACHE_CHECK([whether $CC supports the fallthrough attribute],
+	    [sudo_cv_var_fallthrough_attribute],
+	    [AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+		int main(int argc, char *argv[])
+		{
+		    int num = argc + 1;
+		    switch (num) {
+			case 1:
+			    num = 0;
+			    __attribute__((__fallthrough__));
+			case 0:
+			    num++;
+		    }
+		    return num;
 		}
-		return num;
-	    }
-	]])], [
-	    AC_MSG_RESULT([yes])
-	    CFLAGS="$_CFLAGS -Wimplicit-fallthrough"
-	], [
-	    AC_MSG_RESULT([no])
-	    CFLAGS="$_CFLAGS"
-	])
-
+	    ]])],
+	    [
+		sudo_cv_var_fallthrough_attribute=yes
+	    ],
+	    [
+		sudo_cv_var_fallthrough_attribute=no]
+	    )]
+	)
+	if test X"$sudo_cv_var_fallthrough_attribute" = X"yes"; then
+	    AC_DEFINE(HAVE_FALLTHROUGH_ATTRIBUTE)
+	    CFLAGS="$CFLAGS -Wimplicit-fallthrough"
+	fi
     fi
     if test X"$enable_werror" = X"yes"; then
 	CFLAGS="${CFLAGS} -Werror"
@@ -4891,6 +4896,7 @@ AH_TEMPLATE(HAVE_OPENSSL, [Define to 1 if you are using OpenSSL's TLS and sha2 f
 AH_TEMPLATE(HAVE_GCRYPT, [Define to 1 if you are using gcrypt's sha2 functions.])
 AH_TEMPLATE(HAVE_SSL_CTX_SET_MIN_PROTO_VERSION, [Define to 1 if you have the `SSL_CTX_set_min_proto_version' function or macro.])
 AH_TEMPLATE(SUDOERS_IOLOG_CLIENT, [Define to 1 to compile support for sudo_logsrvd in the sudoers I/O log plugin.])
+AH_TEMPLATE(HAVE_FALLTHROUGH_ATTRIBUTE, [Define to 1 if the compiler supports the fallthrough attribute.])
 
 dnl
 dnl Bits to copy verbatim into config.h.in
diff --git a/include/sudo_compat.h b/include/sudo_compat.h
index 80c007b93..879a0f3ff 100644
--- a/include/sudo_compat.h
+++ b/include/sudo_compat.h
@@ -80,6 +80,12 @@
 # endif
 #endif
 
+#ifdef HAVE_FALLTHROUGH_ATTRIBUTE
+# define FALLTHROUGH 	__attribute__((__fallthrough__))
+#else
+# define FALLTHROUGH 	do { } while (0)
+#endif
+
 /*
  * Given the pointer x to the member m of the struct s, return
  * a pointer to the containing structure.
diff --git a/lib/util/arc4random_buf.c b/lib/util/arc4random_buf.c
index ee4c608ef..76f0fdc02 100644
--- a/lib/util/arc4random_buf.c
+++ b/lib/util/arc4random_buf.c
@@ -50,13 +50,13 @@ sudo_arc4random_buf(void *buf, size_t n)
 		switch (m) {
 		case 4:
 			*cp++ = (val >> 24) & 0xff;
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		case 3:
 			*cp++ = (val >> 16) & 0xff;
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		case 2:
 			*cp++ = (val >> 8) & 0xff;
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		case 1:
 			*cp++ = val & 0xff;
 			break;
diff --git a/lib/util/glob.c b/lib/util/glob.c
index 58af3d383..762e107be 100644
--- a/lib/util/glob.c
+++ b/lib/util/glob.c
@@ -304,7 +304,7 @@ globexp2(const Char *ptr, const Char *pattern, glob_t *pglob,
 				i--;
 				break;
 			}
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		case COMMA:
 			if (i && *pm == COMMA)
 				break;
diff --git a/lib/util/snprintf.c b/lib/util/snprintf.c
index 3874b15a9..6d027ad72 100644
--- a/lib/util/snprintf.c
+++ b/lib/util/snprintf.c
@@ -535,7 +535,7 @@ reswitch:	switch (ch) {
 			if (width == INT_MIN)
 				goto overflow;
 			width = -width;
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		case '-':
 			flags |= LADJUST;
 			goto rflag;
@@ -649,7 +649,7 @@ reswitch:	switch (ch) {
 			break;
 		case 'D':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'd':
 		case 'i':
 			_umax = SARG();
@@ -815,7 +815,7 @@ fp_common:
 #endif /* NO_PRINTF_PERCENT_N */
 		case 'O':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'o':
 			_umax = UARG();
 			base = OCT;
@@ -875,7 +875,7 @@ fp_common:
 			break;
 		case 'U':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'u':
 			_umax = UARG();
 			base = DEC;
@@ -1276,7 +1276,7 @@ reswitch:	switch (ch) {
 			break;
 		case 'D':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'd':
 		case 'i':
 			ADDSARG();
@@ -1316,7 +1316,7 @@ reswitch:	switch (ch) {
 #endif /* NO_PRINTF_PERCENT_N */
 		case 'O':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'o':
 			ADDUARG();
 			break;
@@ -1333,7 +1333,7 @@ reswitch:	switch (ch) {
 			break;
 		case 'U':
 			flags |= LONGINT;
-			/*FALLTHROUGH*/
+			FALLTHROUGH;
 		case 'u':
 		case 'X':
 		case 'x':
diff --git a/lib/util/strtonum.c b/lib/util/strtonum.c
index a76d28bea..d0ce1adb1 100644
--- a/lib/util/strtonum.c
+++ b/lib/util/strtonum.c
@@ -69,7 +69,7 @@ sudo_strtonumx(const char *str, long long minval, long long maxval, char **endp,
 	break;
     case '+':
 	ch = *cp++;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	sign = '+';
 	break;
diff --git a/logsrvd/sendlog.c b/logsrvd/sendlog.c
index 80bf55e67..9a0aad8a8 100644
--- a/logsrvd/sendlog.c
+++ b/logsrvd/sendlog.c
@@ -866,10 +866,10 @@ client_message_completion(struct client_closure *closure)
 	    closure->state = SEND_EXIT;
 	    debug_return_bool(fmt_exit_message(closure));
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SEND_RESTART:
 	closure->state = SEND_IO;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SEND_IO:
 	/* fmt_next_iolog() will advance state on EOF. */
 	if (!fmt_next_iolog(closure))
diff --git a/plugins/python/pyhelpers.c b/plugins/python/pyhelpers.c
index d43c7348b..d20e459cf 100644
--- a/plugins/python/pyhelpers.c
+++ b/plugins/python/pyhelpers.c
@@ -43,7 +43,7 @@ _sudo_printf_default(int msg_type, const char *fmt, ...)
     switch (msg_type & 0xff) {
     case SUDO_CONV_ERROR_MSG:
 	fp = stderr;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SUDO_CONV_INFO_MSG:
 	va_start(ap, fmt);
 	len = vfprintf(ttyfp ? ttyfp : fp, fmt, ap);
diff --git a/plugins/sudoers/auth/pam.c b/plugins/sudoers/auth/pam.c
index dee9ea262..6b4e24970 100644
--- a/plugins/sudoers/auth/pam.c
+++ b/plugins/sudoers/auth/pam.c
@@ -681,7 +681,7 @@ converse(int num_msg, PAM_CONST struct pam_message **msg,
 	switch (pm->msg_style) {
 	    case PAM_PROMPT_ECHO_ON:
 		type = SUDO_CONV_PROMPT_ECHO_ON;
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    case PAM_PROMPT_ECHO_OFF:
 		/* Error out if the last password read was interrupted. */
 		if (getpass_error)
diff --git a/plugins/sudoers/check.c b/plugins/sudoers/check.c
index 915b0d9f1..181b5ed43 100644
--- a/plugins/sudoers/check.c
+++ b/plugins/sudoers/check.c
@@ -121,7 +121,7 @@ check_user_interactive(int validated, int mode, struct getpass_closure *closure)
 	}
 	sudo_debug_printf(SUDO_DEBUG_INFO,
 	    "%s: check user flag overrides time stamp", __func__);
-	/* FALLTHROUGH */
+	FALLTHROUGH;
 
     default:
 	/* Bail out if we are non-interactive and a password is required */
diff --git a/plugins/sudoers/cvtsudoers_ldif.c b/plugins/sudoers/cvtsudoers_ldif.c
index f85d7d096..f61f5ff7b 100644
--- a/plugins/sudoers/cvtsudoers_ldif.c
+++ b/plugins/sudoers/cvtsudoers_ldif.c
@@ -277,7 +277,7 @@ print_member_ldif(FILE *fp, struct sudoers_parse_tree *parse_tree, char *name,
 	    print_attribute_ldif(fp, attr_name, negated ? "!ALL" : "ALL");
 	    break;
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case COMMAND:
 	attr_val = format_cmnd((struct sudo_command *)name, negated);
 	print_attribute_ldif(fp, attr_name, attr_val);
@@ -292,7 +292,7 @@ print_member_ldif(FILE *fp, struct sudoers_parse_tree *parse_tree, char *name,
 	    alias_put(a);
 	    break;
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	len = asprintf(&attr_val, "%s%s", negated ? "!" : "", name);
 	if (len == -1) {
diff --git a/plugins/sudoers/defaults.c b/plugins/sudoers/defaults.c
index 1a4e2b6b3..64f17bb5a 100644
--- a/plugins/sudoers/defaults.c
+++ b/plugins/sudoers/defaults.c
@@ -218,7 +218,7 @@ parse_default_entry(struct sudo_defs_types *def, const char *val, int op,
 	case T_TUPLE:
 	    if (ISSET(def->type, T_BOOL))
 		break;
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case T_LOGFAC:
 	    if (op == true) {
 		/* Use default syslog facility if none specified. */
diff --git a/plugins/sudoers/fmtsudoers.c b/plugins/sudoers/fmtsudoers.c
index 0c935093e..4588dfb03 100644
--- a/plugins/sudoers/fmtsudoers.c
+++ b/plugins/sudoers/fmtsudoers.c
@@ -58,7 +58,7 @@ sudoers_format_member_int(struct sudo_lbuf *lbuf,
 		sudo_lbuf_append(lbuf, "%sALL", negated ? "!" : "");
 		break;
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case COMMAND:
 	    c = (struct sudo_command *) name;
 	    TAILQ_FOREACH(digest, &c->digests, entries) {
@@ -100,7 +100,7 @@ sudoers_format_member_int(struct sudo_lbuf *lbuf,
 		    break;
 		}
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	default:
 	print_word:
 	    /* Do not quote UID/GID, all others get quoted. */
diff --git a/plugins/sudoers/ldap_util.c b/plugins/sudoers/ldap_util.c
index e0df321c3..476caf73c 100644
--- a/plugins/sudoers/ldap_util.c
+++ b/plugins/sudoers/ldap_util.c
@@ -152,7 +152,7 @@ array_to_member_list(void *a, sudo_ldap_iter_t iter)
 		m->type = ALL;
 		break;
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	default:
 	    m->type = WORD;
 	    break;
@@ -222,7 +222,7 @@ host_to_member(char *host)
 	    m->type = ALL;
 	    break;
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	if (is_address(host)) {
 	    m->type = NTWKADDR;
diff --git a/plugins/sudoers/match.c b/plugins/sudoers/match.c
index 905154525..70d6b3e64 100644
--- a/plugins/sudoers/match.c
+++ b/plugins/sudoers/match.c
@@ -98,7 +98,7 @@ user_matches(struct sudoers_parse_tree *parse_tree, const struct passwd *pw,
 		alias_put(a);
 		break;
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case WORD:
 	    if (userpw_matches(m->name, pw->pw_name, pw))
 		matched = !m->negated;
@@ -195,7 +195,7 @@ runaslist_matches(struct sudoers_parse_tree *parse_tree,
 			    alias_put(a);
 			    break;
 			}
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		    case WORD:
 			if (userpw_matches(m->name, runas_pw->pw_name, runas_pw))
 			    user_matched = !m->negated;
@@ -239,7 +239,7 @@ runaslist_matches(struct sudoers_parse_tree *parse_tree,
 			    alias_put(a);
 			    break;
 			}
-			/* FALLTHROUGH */
+			FALLTHROUGH;
 		    case WORD:
 			if (group_matches(m->name, runas_gr))
 			    group_matched = !m->negated;
@@ -352,7 +352,7 @@ host_matches(struct sudoers_parse_tree *parse_tree, const struct passwd *pw,
 		alias_put(a);
 		break;
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case WORD:
 	    if (hostname_matches(shost, lhost, m->name))
 		matched = !m->negated;
@@ -399,7 +399,7 @@ cmnd_matches(struct sudoers_parse_tree *parse_tree, const struct member *m)
 		matched = !m->negated;
 		break;
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case COMMAND:
 	    c = (struct sudo_command *)m->name;
 	    if (command_matches(c->cmnd, c->args, &c->digests))
diff --git a/plugins/sudoers/parse_ldif.c b/plugins/sudoers/parse_ldif.c
index 0bc919c09..ef0c298a6 100644
--- a/plugins/sudoers/parse_ldif.c
+++ b/plugins/sudoers/parse_ldif.c
@@ -368,7 +368,7 @@ role_to_sudoers(struct sudoers_parse_tree *parse_tree, struct sudo_role *role,
 		    m->type = ALL;
 		    break;
 		}
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    default:
 		m->type = WORD;
 		break;
diff --git a/plugins/sudoers/sssd.c b/plugins/sudoers/sssd.c
index b52fec3fa..4ab55c841 100644
--- a/plugins/sudoers/sssd.c
+++ b/plugins/sudoers/sssd.c
@@ -514,7 +514,7 @@ sudo_sss_result_get(struct sudo_nss *nss, struct passwd *pw)
 	break;
     case ENOMEM:
 	sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	sudo_debug_printf(SUDO_DEBUG_ERROR, "handle->fn_send_recv: rc=%d", rc);
 	debug_return_ptr(NULL);
@@ -753,7 +753,7 @@ sudo_sss_getdefs(struct sudo_nss *nss)
 	break;
     case ENOMEM:
 	sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	sudo_debug_printf(SUDO_DEBUG_ERROR,
 	    "handle->fn_send_recv_defaults: rc=%d, sss_error=%u", rc, sss_error);
diff --git a/plugins/sudoers/sudo_printf.c b/plugins/sudoers/sudo_printf.c
index 944280b12..5f0716245 100644
--- a/plugins/sudoers/sudo_printf.c
+++ b/plugins/sudoers/sudo_printf.c
@@ -48,7 +48,7 @@ sudo_printf_int(int msg_type, const char *fmt, ...)
     switch (msg_type & 0xff) {
     case SUDO_CONV_ERROR_MSG:
 	fp = stderr;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SUDO_CONV_INFO_MSG:
 	va_start(ap, fmt);
 	len = vfprintf(ttyfp ? ttyfp : fp, fmt, ap);
diff --git a/plugins/sudoers/sudoreplay.c b/plugins/sudoers/sudoreplay.c
index 54a298b2a..762a41699 100644
--- a/plugins/sudoers/sudoreplay.c
+++ b/plugins/sudoers/sudoreplay.c
@@ -448,7 +448,7 @@ getsize_cb(int fd, int what, void *v)
 	    case -1:
 		if (errno == EAGAIN)
 		    goto another;
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    case 0:
 		goto done;
 	    default:
@@ -487,7 +487,7 @@ getsize_cb(int fd, int what, void *v)
 		goto done;
 	    gc->nums[gc->nums_depth] = 0;
 	    gc->state = NUMBER;
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case NUMBER:
 	    if (!isdigit(ch)) {
 		/* done with number, reparse ch */
diff --git a/plugins/sudoers/timestamp.c b/plugins/sudoers/timestamp.c
index 368edebd4..d25df689d 100644
--- a/plugins/sudoers/timestamp.c
+++ b/plugins/sudoers/timestamp.c
@@ -367,7 +367,7 @@ ts_init_key(struct timestamp_entry *entry, struct passwd *pw, int flags,
     default:
 	/* Unknown time stamp ticket type, treat as tty (should not happen). */
 	sudo_warnx("unknown time stamp ticket type %d", ticket_type);
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case tty:
 	if (user_ttypath != NULL && stat(user_ttypath, &sb) == 0) {
 	    /* tty-based time stamp */
@@ -377,7 +377,7 @@ ts_init_key(struct timestamp_entry *entry, struct passwd *pw, int flags,
 		get_starttime(entry->sid, &entry->start_time);
 	    break;
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case kernel:
     case ppid:
 	/* ppid-based time stamp */
diff --git a/plugins/sudoers/visudo.c b/plugins/sudoers/visudo.c
index d319f8bd4..e019bab80 100644
--- a/plugins/sudoers/visudo.c
+++ b/plugins/sudoers/visudo.c
@@ -811,7 +811,7 @@ whatnow(void)
 	switch (choice) {
 	    case EOF:
 		choice = 'x';
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    case 'e':
 	    case 'x':
 	    case 'Q':
diff --git a/src/conversation.c b/src/conversation.c
index 389c7842a..55c2319c6 100644
--- a/src/conversation.c
+++ b/src/conversation.c
@@ -64,7 +64,7 @@ sudo_conversation(int num_msgs, const struct sudo_conv_message msgs[],
 		goto read_pass;
 	    case SUDO_CONV_PROMPT_MASK:
 		SET(flags, TGP_MASK);
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    case SUDO_CONV_PROMPT_ECHO_OFF:
 		if (ISSET(msg->msg_type, SUDO_CONV_PROMPT_ECHO_OK))
 		    SET(flags, TGP_NOECHO_TRY);
@@ -84,7 +84,7 @@ sudo_conversation(int num_msgs, const struct sudo_conv_message msgs[],
 		break;
 	    case SUDO_CONV_ERROR_MSG:
 		fp = stderr;
-		/* FALLTHROUGH */
+		FALLTHROUGH;
 	    case SUDO_CONV_INFO_MSG:
 		if (msg->msg != NULL) {
 		    size_t len = strlen(msg->msg);
@@ -172,7 +172,7 @@ sudo_conversation_printf(int msg_type, const char *fmt, ...)
     switch (msg_type & 0xff) {
     case SUDO_CONV_ERROR_MSG:
 	fp = stderr;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SUDO_CONV_INFO_MSG:
 	va_start(ap, fmt);
 	len = vfprintf(ttyfp ? ttyfp : fp, fmt, ap);
diff --git a/src/exec_monitor.c b/src/exec_monitor.c
index b781fa858..3c6d10240 100644
--- a/src/exec_monitor.c
+++ b/src/exec_monitor.c
@@ -201,7 +201,7 @@ mon_handle_sigchld(struct monitor_closure *mc)
     switch (pid) {
     case 0:
 	errno = ECHILD;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case -1:
 	sudo_warn(U_("%s: %s"), __func__, "waitpid");
 	debug_return;
diff --git a/src/exec_pty.c b/src/exec_pty.c
index 97a283c58..1b0863938 100644
--- a/src/exec_pty.c
+++ b/src/exec_pty.c
@@ -542,7 +542,7 @@ suspend_sudo(struct exec_closure_pty *ec, int signo)
 	    ret = SIGCONT_FG; /* resume command in foreground */
 	    break;
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case SIGSTOP:
     case SIGTSTP:
 	/* Flush any remaining output and deschedule I/O events. */
@@ -663,7 +663,7 @@ read_callback(int fd, int what, void *v)
 	    /* treat read error as fatal and close the fd */
 	    sudo_debug_printf(SUDO_DEBUG_ERROR,
 		"error reading fd %d: %s", fd, strerror(errno));
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case 0:
 	    /* got EOF or pty has gone away */
 	    if (n == 0) {
@@ -763,7 +763,7 @@ write_callback(int fd, int what, void *v)
 		/* Schedule SIGTTOU to be forwarded to the command. */
 		schedule_signal(iob->ec, SIGTTOU);
 	    }
-	    /* FALLTHROUGH */
+	    FALLTHROUGH;
 	case EAGAIN:
 	    /* not an error */
 	    break;
@@ -1041,7 +1041,7 @@ handle_sigchld_pty(struct exec_closure_pty *ec)
     switch (pid) {
     case 0:
 	errno = ECHILD;
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     case -1:
 	sudo_warn(U_("%s: %s"), __func__, "waitpid");
 	debug_return;
diff --git a/src/parse_args.c b/src/parse_args.c
index f5853b8d8..d37a2839e 100644
--- a/src/parse_args.c
+++ b/src/parse_args.c
@@ -389,7 +389,7 @@ parse_args(int argc, char **argv, int *old_optind, int *nargc, char ***nargv,
 			valid_flags = 0;
 			break;
 		    }
-		    /* FALLTHROUGH */
+		    FALLTHROUGH;
 		case OPT_HOSTNAME:
 		    assert(optarg != NULL);
 		    if (*optarg == '\0')
diff --git a/src/regress/noexec/check_noexec.c b/src/regress/noexec/check_noexec.c
index 82b072e35..db51a74f9 100644
--- a/src/regress/noexec/check_noexec.c
+++ b/src/regress/noexec/check_noexec.c
@@ -161,7 +161,7 @@ try_wordexp(void)
 	    break;
 	}
 	wordfree(&we);
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	printf("%s: FAIL (wordexp) [%d]\n", getprogname(), rc);
 	break;
diff --git a/src/tgetpass.c b/src/tgetpass.c
index 6f6a2732d..ad5c94d60 100644
--- a/src/tgetpass.c
+++ b/src/tgetpass.c
@@ -435,7 +435,7 @@ getln(int fd, char *buf, size_t bufsiz, bool feedback,
 	    *errval = TGP_ERRVAL_NOPASSWORD;
 	    debug_return_str(NULL);
 	}
-	/* FALLTHROUGH */
+	FALLTHROUGH;
     default:
 	debug_return_str_masked(buf);
     }