diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -140,7 +140,7 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CLANG)
   # Note clang-cl is odd and sets both CLANG and MSVC. We base our configuration
   # primarily on our normal Clang one.
   # TODO(bbe) took out -Wmissing-field-initializers for pki - fix and put back or disable only for pki
-  set(C_CXX_FLAGS "-Werror -Wformat=2 -Wsign-compare -Wwrite-strings -Wvla -Wshadow -Wtype-limits")
+  set(C_CXX_FLAGS "-Wformat=2 -Wsign-compare -Wwrite-strings -Wvla -Wshadow -Wtype-limits")
   if(MSVC)
     # clang-cl sets different default warnings than clang. It also treats -Wall
     # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.
@@ -211,8 +211,8 @@ elseif(MSVC)
       )
   string(REPLACE "C" " -wd" MSVC_DISABLED_WARNINGS_STR
                             ${MSVC_DISABLED_WARNINGS_LIST})
-  set(CMAKE_C_FLAGS   "-utf-8 -W4 -WX ${MSVC_DISABLED_WARNINGS_STR}")
-  set(CMAKE_CXX_FLAGS "-utf-8 -W4 -WX ${MSVC_DISABLED_WARNINGS_STR}")
+  set(CMAKE_C_FLAGS   "-utf-8 -W4 ${MSVC_DISABLED_WARNINGS_STR}")
+  set(CMAKE_CXX_FLAGS "-utf-8 -W4 ${MSVC_DISABLED_WARNINGS_STR}")
 endif()
 
 if(WIN32)