diff --git a/llvm/lib/Fuzzer/test/StrstrTest.cpp b/llvm/lib/Fuzzer/test/StrstrTest.cpp
index 90d539b6..dd83953 100644
--- a/llvm/lib/Fuzzer/test/StrstrTest.cpp
+++ b/llvm/lib/Fuzzer/test/StrstrTest.cpp
@@ -9,8 +9,12 @@
 #include <cstdlib>
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  if (Size < 4) return 0;
   std::string s(reinterpret_cast<const char*>(Data), Size);
-  if (strstr(s.c_str(), "FUZZ") && strcasestr(s.c_str(), "aBcD")) {
+  if (strstr(s.c_str(), "FUZZ") &&
+      strcasestr(s.c_str(), "aBcD") &&
+      memmem(s.data(), s.size(), "kuku", 4)
+      ) {
     fprintf(stderr, "BINGO\n");
     exit(1);
   }