diff --git a/llvm/lib/Fuzzer/test/fuzzer.test b/llvm/lib/Fuzzer/test/fuzzer.test
index 9aca950..b42a49b 100644
--- a/llvm/lib/Fuzzer/test/fuzzer.test
+++ b/llvm/lib/Fuzzer/test/fuzzer.test
@@ -116,3 +116,5 @@
 FD_MASK_3-NOT: STREAM_CERR
 FD_MASK_3: INITED
 
+RUN: LLVMFuzzer-SimpleTest -runs=10 --max_len=100 2>&1 | FileCheck %s --check-prefix=DASH_DASH
+DASH_DASH: WARNING: did you mean '-max_len=100' (single dash)?