diff --git a/lib/libutil/passwd.c b/lib/libutil/passwd.c
index 9cc1d481a349..d6c0d9ea4e8f 100644
--- a/lib/libutil/passwd.c
+++ b/lib/libutil/passwd.c
@@ -503,13 +503,21 @@ trim_whitespace(char *line)
 
 	_DIAGASSERT(line != NULL);
 
+	/* Handle empty string */
+	if (strlen(line) == 0)
+		return;
+
 	/* Remove leading spaces */
 	p = line;
 	while (isspace((unsigned char) *p))
 		p++;
 	memmove(line, p, strlen(p) + 1);
 
-	/* Remove trailing spaces */
+	/* Handle empty string after removal of whitespace characters */
+	if (strlen(line) == 0)
+		return;
+
+	/* Remove trailing spaces, line must not be empty string here */
 	p = line + strlen(line) - 1;
 	while (isspace((unsigned char) *p))
 		p--;