diff --git a/tmux.c b/tmux.c
index 5d4fda72..0c161490 100644
--- a/tmux.c
+++ b/tmux.c
@@ -289,8 +289,8 @@ main(int argc, char **argv)
 		 * if not they know that output from UTF-8-capable programs may
 		 * be wrong.
 		 */
-		if ((s = getenv("LC_ALL")) == NULL) {
-			if ((s = getenv("LC_CTYPE")) == NULL)
+		if ((s = getenv("LC_ALL")) == NULL || *s == '\0') {
+			if ((s = getenv("LC_CTYPE")) == NULL || *s == '\0')
 				s = getenv("LANG");
 		}
 		if (s != NULL && (strcasestr(s, "UTF-8") != NULL ||