diff --git a/src/fuzzers/CMakeLists.txt b/src/fuzzers/CMakeLists.txt
index 2cb0fbda2d..b497baf31e 100644
--- a/src/fuzzers/CMakeLists.txt
+++ b/src/fuzzers/CMakeLists.txt
@@ -16,7 +16,8 @@ if ( NOT DEFINED ZEEK_FUZZING_ENGINE AND DEFINED ENV{LIB_FUZZING_ENGINE} )
             # Looks like a linker flag or valid file, use it
             set(ZEEK_FUZZING_ENGINE "$ENV{LIB_FUZZING_ENGINE}" CACHE INTERNAL "" FORCE)
         else ()
-            message(FATAL_ERROR "Invalid LIB_FUZZING_ENGINE: '$ENV{LIB_FUZZING_ENGINE}'")
+            message(WARNING "$ENV{LIB_FUZZING_ENGINE} does not exist, assume libFuzzer")
+            set(ZEEK_FUZZING_ENGINE "-fsanitize=fuzzer" CACHE INTERNAL "" FORCE)
         endif ()
     endif ()
 endif ()