diff --git a/lib/iolog/regress/fuzz/fuzz_iolog_json.c b/lib/iolog/regress/fuzz/fuzz_iolog_json.c
index 4f39615fb..465e405a6 100644
--- a/lib/iolog/regress/fuzz/fuzz_iolog_json.c
+++ b/lib/iolog/regress/fuzz/fuzz_iolog_json.c
@@ -66,6 +66,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/lib/iolog/regress/fuzz/fuzz_iolog_legacy.c b/lib/iolog/regress/fuzz/fuzz_iolog_legacy.c
index c1def41fa..c63b036dd 100644
--- a/lib/iolog/regress/fuzz/fuzz_iolog_legacy.c
+++ b/lib/iolog/regress/fuzz/fuzz_iolog_legacy.c
@@ -64,6 +64,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/lib/iolog/regress/fuzz/fuzz_iolog_timing.c b/lib/iolog/regress/fuzz/fuzz_iolog_timing.c
index 98c3b585a..cd520709e 100644
--- a/lib/iolog/regress/fuzz/fuzz_iolog_timing.c
+++ b/lib/iolog/regress/fuzz/fuzz_iolog_timing.c
@@ -45,6 +45,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/lib/util/regress/fuzz/fuzz_sudo_conf.c b/lib/util/regress/fuzz/fuzz_sudo_conf.c
index ff3980777..96e8015d0 100644
--- a/lib/util/regress/fuzz/fuzz_sudo_conf.c
+++ b/lib/util/regress/fuzz/fuzz_sudo_conf.c
@@ -37,6 +37,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/logsrvd/regress/fuzz/fuzz_logsrvd_conf.c b/logsrvd/regress/fuzz/fuzz_logsrvd_conf.c
index d92cf3942..09787eca0 100644
--- a/logsrvd/regress/fuzz/fuzz_logsrvd_conf.c
+++ b/logsrvd/regress/fuzz/fuzz_logsrvd_conf.c
@@ -47,6 +47,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/plugins/sudoers/regress/fuzz/fuzz_policy.c b/plugins/sudoers/regress/fuzz/fuzz_policy.c
index bddb6e315..f568e594f 100644
--- a/plugins/sudoers/regress/fuzz/fuzz_policy.c
+++ b/plugins/sudoers/regress/fuzz/fuzz_policy.c
@@ -133,6 +133,25 @@ static int
 fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
     struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
 {
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
     return 0;
 }
 
diff --git a/plugins/sudoers/regress/fuzz/fuzz_sudoers.c b/plugins/sudoers/regress/fuzz/fuzz_sudoers.c
index fb509dd70..84a101994 100644
--- a/plugins/sudoers/regress/fuzz/fuzz_sudoers.c
+++ b/plugins/sudoers/regress/fuzz/fuzz_sudoers.c
@@ -69,7 +69,6 @@ fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
 
     for (n = 0; n < num_msgs; n++) {
 	const struct sudo_conv_message *msg = &msgs[n];
-	FILE *fp = stdout;
 
 	switch (msg->msg_type & 0xff) {
 	    case SUDO_CONV_PROMPT_ECHO_ON:
@@ -78,18 +77,8 @@ fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
 		/* input not supported */
 		return -1;
 	    case SUDO_CONV_ERROR_MSG:
-		fp = stderr;
-		FALLTHROUGH;
 	    case SUDO_CONV_INFO_MSG:
-		if (msg->msg != NULL) {
-		    size_t len = strlen(msg->msg);
-
-		    if (len == 0)
-			break;
-
-		    if (fwrite(msg->msg, 1, len, fp) == 0 || fputc('\n', fp) == EOF)
-			return -1;
-		}
+		/* no output for fuzzers */
 		break;
 	    default:
 		return -1;
@@ -197,6 +186,7 @@ LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
     setprogname("fuzz_sudoers");
     sudoers_debug_register(getprogname(), NULL);
+    sudo_warn_set_conversation(fuzz_conversation);
 
     /* Sudoers locale setup. */
     sudoers_initlocale(setlocale(LC_ALL, ""), "C");
@@ -352,11 +342,9 @@ LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	    /* Match again as a pseudo-command (list, validate, etc). */
 	    sudoers_lookup(&snl, sudo_user.pw, &cmnd_status, true);
 
-#if 0
 	    /* Display privileges. */
 	    display_privs(&snl, sudo_user.pw, false);
 	    display_privs(&snl, sudo_user.pw, true);
-#endif
 	}
 
 	/* Expand tildes in runcwd and runchroot. */
diff --git a/plugins/sudoers/regress/fuzz/fuzz_sudoers_ldif.c b/plugins/sudoers/regress/fuzz/fuzz_sudoers_ldif.c
index 70c2a3ce7..2cfa16175 100644
--- a/plugins/sudoers/regress/fuzz/fuzz_sudoers_ldif.c
+++ b/plugins/sudoers/regress/fuzz/fuzz_sudoers_ldif.c
@@ -82,6 +82,32 @@ open_data(const uint8_t *data, size_t size)
 #endif
 }
 
+static int
+fuzz_conversation(int num_msgs, const struct sudo_conv_message msgs[],
+    struct sudo_conv_reply replies[], struct sudo_conv_callback *callback)
+{
+    int n;
+
+    for (n = 0; n < num_msgs; n++) {
+	const struct sudo_conv_message *msg = &msgs[n];
+
+	switch (msg->msg_type & 0xff) {
+	    case SUDO_CONV_PROMPT_ECHO_ON:
+	    case SUDO_CONV_PROMPT_MASK:
+	    case SUDO_CONV_PROMPT_ECHO_OFF:
+		/* input not supported */
+		return -1;
+	    case SUDO_CONV_ERROR_MSG:
+	    case SUDO_CONV_INFO_MSG:
+		/* no output for fuzzers */
+		break;
+	    default:
+		return -1;
+	}
+    }
+    return 0;
+}
+
 int
 LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {
@@ -98,6 +124,7 @@ LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 
     setprogname("fuzz_sudoers_ldif");
     sudoers_debug_register(getprogname(), NULL);
+    sudo_warn_set_conversation(fuzz_conversation);
 
     /* Initialize defaults and parse LDIF-format sudoers. */
     init_defaults();