diff --git a/lib/libc/stdlib/getopt_long.c b/lib/libc/stdlib/getopt_long.c
index 9534a2aff67e..4d92fd0cd45d 100644
--- a/lib/libc/stdlib/getopt_long.c
+++ b/lib/libc/stdlib/getopt_long.c
@@ -481,6 +481,8 @@ getopt_internal(int nargc, char * const *nargv, const char *options,
 #endif
 		if (*place == '-') {
 			place++;		/* --foo long option */
+			if (*place == '\0')
+				return (BADARG);	/* malformed option */
 #ifdef GNU_COMPATIBLE
 			dash_prefix = DD_PREFIX;
 #endif