--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -962,33 +962,22 @@ def compiler(language, host_or_target, c
 
         # If you want to bump the version check here search for
         # builtin_bitreverse8 above, and see the associated comment.
         if info.type == 'clang' and not info.version:
             raise FatalCheckError(
                 'Only clang/llvm 3.9 or newer is supported.')
 
         if info.type == 'msvc':
-            if info.version < '19.13.26128':
+            if info.version < '19.15.26726':
                 raise FatalCheckError(
                     'This version (%s) of the MSVC compiler is not '
                     'supported.\n'
-                    'You must install Visual C++ 2017 Update 6 or '
-                    'Update 8 or later in order to build.\n'
-                    'See https://developer.mozilla.org/en/'
-                    'Windows_Build_Prerequisites' % info.version)
-
-            # MSVC version 15.7 and the previews for 15.8, at least,
-            # can't build Firefox.
-            if info.version >= '19.14.0' and info.version < '19.15.0':
-                raise FatalCheckError(
-                    'This version (%s) of the MSVC compiler is not '
-                    'supported due to compiler bugs.\n'
-                    'You must install Visual C++ 2017 Update 6 or '
-                    'Update 8 or later in order to build.\n'
+                    'You must install Visual C++ 2017 Update 8 or '
+                    'later in order to build.\n'
                     'See https://developer.mozilla.org/en/'
                     'Windows_Build_Prerequisites' % info.version)
 
         if info.flags:
             raise FatalCheckError(
                 'Unknown compiler or compiler not supported.')
 
         return namespace(

--- a/python/mozbuild/mozbuild/test/configure/test_toolchain_configure.py
+++ b/python/mozbuild/mozbuild/test/configure/test_toolchain_configure.py
@@ -896,65 +896,28 @@ class WindowsToolchainTest(BaseToolchain
         '/usr/bin/clang': DEFAULT_CLANG + CLANG_PLATFORM_X86_WIN,
         '/usr/bin/clang++': DEFAULT_CLANGXX + CLANG_PLATFORM_X86_WIN,
         '/usr/bin/clang-3.6': CLANG_3_6 + CLANG_PLATFORM_X86_WIN,
         '/usr/bin/clang++-3.6': CLANGXX_3_6 + CLANG_PLATFORM_X86_WIN,
         '/usr/bin/clang-3.3': CLANG_3_3 + CLANG_PLATFORM_X86_WIN,
         '/usr/bin/clang++-3.3': CLANGXX_3_3 + CLANG_PLATFORM_X86_WIN,
     }
 
-    VS_2013u2_RESULT = (
-        'This version (18.00.30501) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2013u3_RESULT = (
-        'This version (18.00.30723) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2015_RESULT = (
-        'This version (19.00.23026) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2015u1_RESULT = (
-        'This version (19.00.23506) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2015u2_RESULT = (
-        'This version (19.00.23918) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
+    VS_FAILURE_MESSAGE = (
+        'This version (%s) of the MSVC compiler is not supported.\nYou must'
+        ' install Visual C++ 2017 Update 8 or later in order to build.\n'
         'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2015u3_RESULT = (
-        'This version (19.00.24213) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2017u4_RESULT = (
-        'This version (19.11.25547) of the MSVC compiler is not supported.\n'
-        'You must install Visual C++ 2017 Update 6 or Update 8 or later'
-        ' in order to build.\n'
-        'See https://developer.mozilla.org/en/Windows_Build_Prerequisites')
-    VS_2017u6_RESULT = CompilerResult(
-        flags=[],
-        version='19.13.26128',
-        type='msvc',
-        compiler='/opt/VS_2017u6/bin/cl',
-        language='C',
-    )
-    VSXX_2017u6_RESULT = CompilerResult(
-        flags=[],
-        version='19.13.26128',
-        type='msvc',
-        compiler='/opt/VS_2017u6/bin/cl',
-        language='C++',
-    )
+    VS_2013u2_RESULT = VS_FAILURE_MESSAGE % '18.00.30501'
+    VS_2013u3_RESULT = VS_FAILURE_MESSAGE % '18.00.30723'
+    VS_2015_RESULT = VS_FAILURE_MESSAGE % '19.00.23026'
+    VS_2015u1_RESULT = VS_FAILURE_MESSAGE % '19.00.23506'
+    VS_2015u2_RESULT = VS_FAILURE_MESSAGE % '19.00.23918'
+    VS_2015u3_RESULT = VS_FAILURE_MESSAGE % '19.00.24213'
+    VS_2017u4_RESULT = VS_FAILURE_MESSAGE % '19.11.25547'
+    VS_2017u6_RESULT = VS_FAILURE_MESSAGE % '19.13.26128'
     VS_2017u8_RESULT = CompilerResult(
         flags=[],
         version='19.15.26726',
         type='msvc',
         compiler='/usr/bin/cl',
         language='C',
     )
     VSXX_2017u8_RESULT = CompilerResult(
@@ -1000,25 +963,23 @@ class WindowsToolchainTest(BaseToolchain
             k: v for k, v in self.PATHS.iteritems()
             if os.path.basename(k) != 'clang-cl'
         }
         self.do_toolchain_test(paths, {
             'c_compiler': self.VS_2017u8_RESULT,
             'cxx_compiler': self.VSXX_2017u8_RESULT,
         })
 
+    def test_unsupported_msvc(self):
         self.do_toolchain_test(self.PATHS, {
             'c_compiler': self.VS_2017u6_RESULT,
-            'cxx_compiler': self.VSXX_2017u6_RESULT,
         }, environ={
             'CC': '/opt/VS_2017u6/bin/cl',
-            'CXX': '/opt/VS_2017u6/bin/cl',
         })
 
-    def test_unsupported_msvc(self):
         self.do_toolchain_test(self.PATHS, {
             'c_compiler': self.VS_2017u4_RESULT,
         }, environ={
             'CC': '/opt/VS_2017u4/bin/cl',
         })
 
         self.do_toolchain_test(self.PATHS, {
             'c_compiler': self.VS_2015u3_RESULT,