diff --git a/src/core/wee-string.c b/src/core/wee-string.c
index b813669f0..119ac6fc3 100644
--- a/src/core/wee-string.c
+++ b/src/core/wee-string.c
@@ -560,7 +560,7 @@ string_strip (const char *string, int left, int right, const char *chars)
     if (!string)
         return NULL;
 
-    if (!string[0])
+    if (!string[0] || !chars)
         return strdup (string);
 
     ptr_start = string;