diff --git a/CMakeLists.txt b/CMakeLists.txt
index 92669f9..7d2e1bf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,6 +76,14 @@
 message(STATUS "Using python3")
 find_package(PythonInterp 3 REQUIRED)
 
+# CMake < 3.15 sets /W3 in CMAKE_CXX_FLAGS. Remove it if it's there.
+# See https://gitlab.kitware.com/cmake/cmake/-/issues/18317
+if (MSVC)
+    if (CMAKE_CXX_FLAGS MATCHES "/W3")
+        string(REPLACE "/W3" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    endif()
+endif()
+
 if (${TINT_CHECK_CHROMIUM_STYLE})
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Xclang -add-plugin -Xclang find-bad-constructs")
 endif()
@@ -186,8 +194,10 @@
       /W4
       /WX
       /wd4068
+      /wd4127
       /wd4244
       /wd4267
+      /wd4458
       /wd4514
       /wd4571
       /wd4625
diff --git a/src/writer/spirv/builder_discard_test.cc b/src/writer/spirv/builder_discard_test.cc
index 938a130..6784893 100644
--- a/src/writer/spirv/builder_discard_test.cc
+++ b/src/writer/spirv/builder_discard_test.cc
@@ -28,7 +28,7 @@
   spirv::Builder& b = Build();
 
   b.push_function(Function{});
-  EXPECT_EQ(b.GenerateStatement(expr), 1u) << b.error();
+  EXPECT_TRUE(b.GenerateStatement(expr)) << b.error();
   EXPECT_EQ(DumpInstructions(b.functions()[0].instructions()), R"(OpKill
 )");
 }
diff --git a/src/writer/spirv/builder_function_decoration_test.cc b/src/writer/spirv/builder_function_decoration_test.cc
index 34b8e89..f46ccfb 100644
--- a/src/writer/spirv/builder_function_decoration_test.cc
+++ b/src/writer/spirv/builder_function_decoration_test.cc
@@ -65,7 +65,8 @@
   EXPECT_EQ(preamble[0].opcode(), spv::Op::OpEntryPoint);
 
   ASSERT_GE(preamble[0].operands().size(), 3u);
-  EXPECT_EQ(preamble[0].operands()[0].to_i(), params.model);
+  EXPECT_EQ(preamble[0].operands()[0].to_i(),
+            static_cast<uint32_t>(params.model));
 }
 INSTANTIATE_TEST_SUITE_P(
     BuilderTest,