diff --git a/src/stdlib/SDL_string.c b/src/stdlib/SDL_string.c
index b8536e81e..1a5e3422b 100644
--- a/src/stdlib/SDL_string.c
+++ b/src/stdlib/SDL_string.c
@@ -858,9 +858,13 @@ SDL_strncasecmp(const char *str1, const char *str2, size_t maxlen)
         ++str2;
         --maxlen;
     }
-    a = SDL_tolower((unsigned char) *str1);
-    b = SDL_tolower((unsigned char) *str2);
-    return (int) ((unsigned char) a - (unsigned char) b);
+    if (maxlen == 0) {
+        return 0;
+    } else {
+        a = SDL_tolower((unsigned char) *str1);
+        b = SDL_tolower((unsigned char) *str2);
+        return (int) ((unsigned char) a - (unsigned char) b);
+    }
 }
 #endif