diff --git a/include/sudo_util.h b/include/sudo_util.h
index 8212a3b16..3702b9705 100644
--- a/include/sudo_util.h
+++ b/include/sudo_util.h
@@ -262,7 +262,8 @@ sudo_dso_public bool sudo_regex_compile_v1(void *v, const char *pattern, const c
 
 /* roundup.c */
 sudo_dso_public unsigned int sudo_pow2_roundup_v1(unsigned int len);
-#define sudo_pow2_roundup(_a) sudo_pow2_roundup_v1((_a))
+sudo_dso_public size_t sudo_pow2_roundup_v2(size_t len);
+#define sudo_pow2_roundup(_a) sudo_pow2_roundup_v2((_a))
 
 /* secure_path.c */
 #define SUDO_PATH_SECURE		0
diff --git a/lib/util/lbuf.c b/lib/util/lbuf.c
index b659ff1a7..f8851ee86 100644
--- a/lib/util/lbuf.c
+++ b/lib/util/lbuf.c
@@ -79,7 +79,7 @@ sudo_lbuf_expand(struct sudo_lbuf *lbuf, unsigned int extra)
     }
 
     if (lbuf->len + extra + 1 > lbuf->size) {
-	unsigned int new_size = sudo_pow2_roundup(lbuf->len + extra + 1);
+	size_t new_size = sudo_pow2_roundup(lbuf->len + extra + 1);
 	char *new_buf;
 
 	if (new_size < lbuf->size) {
diff --git a/lib/util/roundup.c b/lib/util/roundup.c
index 0e7e8fdcd..7caf8b454 100644
--- a/lib/util/roundup.c
+++ b/lib/util/roundup.c
@@ -30,10 +30,20 @@
 /*
  * Round 32-bit unsigned length to the next highest power of two.
  * Always returns at least 64.
- * Algorithm from bit twiddling hacks.
  */
 unsigned int
 sudo_pow2_roundup_v1(unsigned int len)
+{
+    return (unsigned int)sudo_pow2_roundup_v2((size_t)len);
+}
+
+/*
+ * Round a size_t length to the next highest power of two.
+ * Always returns at least 64.
+ * Algorithm from bit twiddling hacks.
+ */
+size_t
+sudo_pow2_roundup_v2(size_t len)
 {
     if (len < 64)
 	return 64;
@@ -43,6 +53,8 @@ sudo_pow2_roundup_v1(unsigned int len)
     len |= len >> 4;
     len |= len >> 8;
     len |= len >> 16;
-    len++;
-    return len;
+#ifdef __LP64__
+    len |= len >> 32;
+#endif
+    return ++len;
 }
diff --git a/lib/util/util.exp.in b/lib/util/util.exp.in
index 54bf365f5..d8ceeb51a 100644
--- a/lib/util/util.exp.in
+++ b/lib/util/util.exp.in
@@ -126,6 +126,7 @@ sudo_parse_gids_v1
 sudo_parseln_v1
 sudo_parseln_v2
 sudo_pow2_roundup_v1
+sudo_pow2_roundup_v2
 sudo_rcstr_addref
 sudo_rcstr_alloc
 sudo_rcstr_delref
diff --git a/logsrvd/logsrv_util.c b/logsrvd/logsrv_util.c
index 118b81bb4..95ec86e64 100644
--- a/logsrvd/logsrv_util.c
+++ b/logsrvd/logsrv_util.c
@@ -62,9 +62,9 @@ expand_buf(struct connection_buffer *buf, unsigned int needed)
 
     if (buf->size < needed) {
 	/* Expand buffer. */
-	const unsigned int newsize = sudo_pow2_roundup(needed);
+	const size_t newsize = sudo_pow2_roundup(needed);
 	sudo_debug_printf(SUDO_DEBUG_INFO|SUDO_DEBUG_LINENO,
-	    "expanding buffer from %u to %u", buf->size, newsize);
+	    "expanding buffer from %u to %zu", buf->size, newsize);
 	if (newsize < needed) {
 	    /* overflow */
 	    errno = ENOMEM;
diff --git a/logsrvd/logsrvd.c b/logsrvd/logsrvd.c
index 9fc93c777..77e9252f8 100644
--- a/logsrvd/logsrvd.c
+++ b/logsrvd/logsrvd.c
@@ -302,7 +302,7 @@ get_free_buf(size_t len, struct connection_closure *closure)
     }
 
     if (len > buf->size) {
-	const unsigned int new_size = sudo_pow2_roundup(len);
+	const size_t new_size = sudo_pow2_roundup(len);
 	if (new_size < len) {
 	    /* overflow */
 	    errno = ENOMEM;
diff --git a/plugins/sudoers/log_client.c b/plugins/sudoers/log_client.c
index 5017f581d..d30353fbb 100644
--- a/plugins/sudoers/log_client.c
+++ b/plugins/sudoers/log_client.c
@@ -732,7 +732,7 @@ fmt_client_message(struct client_closure *closure, ClientMessage *msg)
 
     /* Resize buffer as needed. */
     if (len > buf->size) {
-	const unsigned int new_size = sudo_pow2_roundup(len);
+	const size_t new_size = sudo_pow2_roundup(len);
 	if (new_size < len) {
 	    /* overflow */
 	    errno = ENOMEM;
@@ -1639,7 +1639,7 @@ expand_buf(struct connection_buffer *buf, unsigned int needed)
 
     if (buf->size < needed) {
 	/* Expand buffer. */
-	const unsigned int newsize = sudo_pow2_roundup(needed);
+	const size_t newsize = sudo_pow2_roundup(needed);
 	if (newsize < needed) {
 	    /* overflow */
 	    errno = ENOMEM;