diff --git a/src/Makefile b/src/Makefile
index 7a8ba94aa1c78079c40dbd499a19f02741dcb371..97a6322a58ce3d2aa956f591ab6b97f2f8162ab3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -18,7 +18,7 @@ CC=$(CLANG)
 SAN_FLAGS ?= -fsanitize=address -fno-omit-frame-pointer -DPASSBOOK_FUZZ
 FUZZ_FLAGS ?= -DPASSBOOK_LIBFUZZER -fsanitize=fuzzer,address -fno-omit-frame-pointer -DPASSBOOK_FUZZ
 NO_STRICT_OVERFLOW_CFLAGS ?= -fwrapv -fno-strict-overflow -Wstrict-overflow
-COV_FLAGS ?= -fprofile-instr-generate -fcoverage-mapping
+COV_FLAGS ?= -fprofile-instr-generate -fcoverage-mapping -DPASSBOOK_FUZZ
 
 default: $(TARGETS)