Index: lib/Fuzzer/CMakeLists.txt
===================================================================
--- lib/Fuzzer/CMakeLists.txt
+++ lib/Fuzzer/CMakeLists.txt
@@ -2,6 +2,12 @@
 # Disable the coverage and sanitizer instrumentation for the fuzzer itself.
 set(CMAKE_CXX_FLAGS "${LIBFUZZER_FLAGS_BASE} -fno-sanitize=all -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters -Werror")
 if( LLVM_USE_SANITIZE_COVERAGE )
+  if(NOT "${LLVM_USE_SANITIZER}" STREQUAL "Address")
+    message(FATAL_ERROR
+      "LLVM_USE_SANITIZER must be set to Address"
+      " to build LibFuzzer"
+      )
+  endif()
   add_library(LLVMFuzzerNoMainObjects OBJECT
     FuzzerCrossOver.cpp
     FuzzerTraceState.cpp