diff --git a/src/goodbyedpi.c b/src/goodbyedpi.c
index 016e9184..18c1c282 100644
--- a/src/goodbyedpi.c
+++ b/src/goodbyedpi.c
@@ -182,10 +182,7 @@ static char *filter_passive_string = NULL;
 static void *memmem(const void *haystack, size_t haystack_len, 
     const void * const needle, const size_t needle_len)
 {
-    if (haystack == NULL) return NULL; // or assert(haystack != NULL);
-    if (haystack_len == 0) return NULL;
-    if (needle == NULL) return NULL; // or assert(needle != NULL);
-    if (needle_len == 0) return NULL;
+    if (needle_len > haystack_len) return NULL;
     
     for (const char *h = haystack;
             haystack_len >= needle_len;