diff --git a/CMakeLists.txt b/CMakeLists.txt
index eda6a72..386966f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -58,6 +58,10 @@ elseif(UNIX)
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--build-id")
 endif()
 
+if (MSVC)
+  add_compile_options(/wd4146 -D_CRT_SECURE_NO_WARNINGS)
+endif()
+
 enable_testing()
 
 add_library(port
diff --git a/upb/json_decode.c b/upb/json_decode.c
index 953d238..5185ffd 100644
--- a/upb/json_decode.c
+++ b/upb/json_decode.c
@@ -1138,7 +1138,7 @@ static void jsondec_struct(jsondec *d, upb_msg *msg, const upb_msgdef *m) {
 static void jsondec_wellknownvalue(jsondec *d, upb_msg *msg,
                                    const upb_msgdef *m) {
   upb_msgval val;
-  const upb_fielddef *f;
+  const upb_fielddef *f = NULL;
   upb_msg *submsg;
 
   switch (jsondec_peek(d)) {