diff --git a/config/config.mk b/config/config.mk
index 28595e711910..a31645da013f 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -106,13 +106,13 @@ VERSION_NUMBER		= 50
 CONFIG_TOOLS	= $(MOZ_BUILD_ROOT)/config
 AUTOCONF_TOOLS	= $(MOZILLA_DIR)/build/autoconf
 
-ifdef _MSC_VER
+ifeq (msvc,$(CC_TYPE))
 # clang-cl is smart enough to generate dependencies directly.
-ifeq (,$(CLANG_CL)$(MOZ_USING_SCCACHE))
+ifeq (,$(MOZ_USING_SCCACHE))
 CC_WRAPPER ?= $(call py_action,cl)
 CXX_WRAPPER ?= $(call py_action,cl)
-endif # CLANG_CL/MOZ_USING_SCCACHE
-endif # _MSC_VER
+endif # MOZ_USING_SCCACHE
+endif # CC_TYPE
 
 CC := $(CC_WRAPPER) $(CC)
 CXX := $(CXX_WRAPPER) $(CXX)
@@ -300,7 +300,7 @@ WIN32_EXE_LDFLAGS	+= $(WIN32_CONSOLE_EXE_LDFLAGS)
 endif
 endif # WINNT
 
-ifdef _MSC_VER
+ifneq (,$(filter msvc clang-cl,$(CC_TYPE)))
 ifeq ($(CPU_ARCH),x86_64)
 # Normal operation on 64-bit Windows needs 2 MB of stack. (Bug 582910)
 # ASAN requires 6 MB of stack.
diff --git a/config/rules.mk b/config/rules.mk
index f0dbbfafc3c4..d31d77269908 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -674,7 +674,7 @@ endif
 $(HOST_SHARED_LIBRARY): Makefile
 	$(REPORT_BUILD)
 	$(RM) $@
-ifdef _MSC_VER
+ifneq (,$(filter msvc clang-cl,$(HOST_CC_TYPE)))
 	$(HOST_LINKER) -NOLOGO -DLL -OUT:$@ $($(notdir $@)_OBJS) $(HOST_CXX_LDFLAGS) $(HOST_LDFLAGS) $(HOST_LINKER_LIBPATHS) $(HOST_LIBS) $(HOST_EXTRA_LIBS)
 else
 	$(HOST_CXX) $(HOST_OUTOPTION)$@ $($(notdir $@)_OBJS) $(HOST_CXX_LDFLAGS) $(HOST_LDFLAGS) $(HOST_LIBS) $(HOST_EXTRA_LIBS)
diff --git a/js/src/old-configure.in b/js/src/old-configure.in
index a2b9c101550a..624c60956607 100644
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -159,21 +159,17 @@ case "$target" in
         _MSVC_VER_FILTER='s|.*[^!-~]([0-9]+\.[0-9]+\.[0-9]+(\.[0-9]+)?).*|\1|p'
         changequote([,])
 
-        _MSC_VER=`echo ${CC_VERSION} | cut -c 1-2,4-5`
-
         AC_DEFINE(_CRT_SECURE_NO_WARNINGS)
         AC_DEFINE(_CRT_NONSTDC_NO_WARNINGS)
         AC_DEFINE(_USE_MATH_DEFINES) # Otherwise MSVC's math.h doesn't #define M_PI.
 
-        if test "$_MSC_VER" -ge "1910"; then # VS2017+
-            # C5038: Enable initializer list order warnings
-            # The -w1#### flag treats warning C#### as if it was a warning level
-            # 1 warning, and thus enables it because we enable /W3 warnings. We
-            # don't use -we#### because it would enable warning C#### but treat
-            # it as an error, even in third-party code.
-            # https://docs.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level
-            CXXFLAGS="$CXXFLAGS -w15038"
-        fi
+        # C5038: Enable initializer list order warnings
+        # The -w1#### flag treats warning C#### as if it was a warning level
+        # 1 warning, and thus enables it because we enable /W3 warnings. We
+        # don't use -we#### because it would enable warning C#### but treat
+        # it as an error, even in third-party code.
+        # https://docs.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level
+        CXXFLAGS="$CXXFLAGS -w15038"
 
         _CC_SUITE=14
         MSVC_C_RUNTIME_DLL=vcruntime140.dll
@@ -266,8 +262,6 @@ if test -n "$SBCONF"; then
 fi
 AC_SUBST(QEMU_CANT_RUN_JS_SHELL)
 
-AC_SUBST(_MSC_VER)
-
 AC_SUBST(GNU_CC)
 AC_SUBST(GNU_CXX)
 
diff --git a/old-configure.in b/old-configure.in
index 95b3a5e7e684..4be91798156b 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -160,8 +160,6 @@ case "$target" in
         _MSVC_VER_FILTER='s|.*[^!-~]([0-9]+\.[0-9]+\.[0-9]+(\.[0-9]+)?).*|\1|p'
         changequote([,])
 
-        _MSC_VER=`echo ${CC_VERSION} | cut -c 1-2,4-5`
-
         AC_DEFINE(_CRT_SECURE_NO_WARNINGS)
         AC_DEFINE(_CRT_NONSTDC_NO_WARNINGS)
         AC_DEFINE(_USE_MATH_DEFINES) # Otherwise MSVC's math.h doesn't #define M_PI.
@@ -175,15 +173,13 @@ case "$target" in
             AC_DEFINE(MSVC_HAS_DIA_SDK)
         fi
 
-        if test "$_MSC_VER" -ge "1910"; then # VS2017+
-            # C5038: Enable initializer list order warnings
-            # The -w1#### flag treats warning C#### as if it was a warning level
-            # 1 warning, and thus enables it because we enable /W3 warnings. We
-            # don't use -we#### because it would enable warning C#### but treat
-            # it as an error, even in third-party code.
-            # https://docs.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level
-            CXXFLAGS="$CXXFLAGS -w15038"
-        fi
+        # C5038: Enable initializer list order warnings
+        # The -w1#### flag treats warning C#### as if it was a warning level
+        # 1 warning, and thus enables it because we enable /W3 warnings. We
+        # don't use -we#### because it would enable warning C#### but treat
+        # it as an error, even in third-party code.
+        # https://docs.microsoft.com/en-us/cpp/build/reference/compiler-option-warning-level
+        CXXFLAGS="$CXXFLAGS -w15038"
 
         # C5026: move constructor was implicitly defined as deleted
         CXXFLAGS="$CXXFLAGS -wd5026"
@@ -295,8 +291,6 @@ fi
 
 fi # COMPILE_ENVIRONMENT
 
-AC_SUBST(_MSC_VER)
-
 AC_SUBST(GNU_CC)
 AC_SUBST(GNU_CXX)
 
diff --git a/python/mozbuild/mozbuild/action/check_binary.py b/python/mozbuild/mozbuild/action/check_binary.py
index aea4d36d3e25..38c91d5816df 100644
--- a/python/mozbuild/mozbuild/action/check_binary.py
+++ b/python/mozbuild/mozbuild/action/check_binary.py
@@ -172,7 +172,7 @@ def check_nsmodules(target, binary):
     if target is HOST or not is_libxul(binary):
         raise Skip()
     symbols = []
-    if buildconfig.substs.get('_MSC_VER'):
+    if buildconfig.substs.get('CC_TYPE') in ('msvc', 'clang-cl'):
         for line in get_output('dumpbin.exe', '-exports', binary):
             data = line.split(None, 3)
             if data and len(data) == 4 and data[0].isdigit() and \
@@ -240,7 +240,7 @@ def check_nsmodules(target, binary):
     # MSVC linker, when doing incremental linking, adds padding when
     # merging sections. Allow there to be more space between the NSModule
     # symbols, as long as they are in the right order.
-    test_msvc = (buildconfig.substs.get('_MSC_VER') and \
+    test_msvc = (buildconfig.substs.get('CC_TYPE') in ('msvc', 'clang-cl') and \
         buildconfig.substs.get('DEVELOPER_OPTIONS'))
     test_clang = (buildconfig.substs.get('CC_TYPE') == 'clang' and \
         buildconfig.substs.get('OS_ARCH') == 'WINNT')
diff --git a/python/mozbuild/mozbuild/frontend/gyp_reader.py b/python/mozbuild/mozbuild/frontend/gyp_reader.py
index 4d106f72d152..0dabdf249778 100644
--- a/python/mozbuild/mozbuild/frontend/gyp_reader.py
+++ b/python/mozbuild/mozbuild/frontend/gyp_reader.py
@@ -243,7 +243,7 @@ def process_gyp_result(gyp_result, gyp_dir_attrs, path, config, output,
             context['UNIFIED_SOURCES'] = alphabetical_sorted(unified_sources)
 
             defines = target_conf.get('defines', [])
-            if bool(config.substs['_MSC_VER']) and no_chromium:
+            if config.substs['CC_TYPE'] in ('msvc', 'clang-cl') and no_chromium:
                 msvs_settings = gyp.msvs_emulation.MsvsSettings(spec, {})
                 defines.extend(msvs_settings.GetComputedDefines(c))
             for define in defines:
@@ -380,7 +380,7 @@ class GypProcessor(object):
         # gyp expects plain str instead of unicode. The frontend code gives us
         # unicode strings, so convert them.
         path = encode(path)
-        if bool(config.substs['_MSC_VER']):
+        if config.substs['CC_TYPE'] in ('msvc', 'clang-cl'):
             # This isn't actually used anywhere in this generator, but it's needed
             # to override the registry detection of VC++ in gyp.
             os.environ['GYP_MSVS_OVERRIDE_PATH'] = 'fake_path'