--- a/gfx/2d/moz.build
+++ b/gfx/2d/moz.build
@@ -75,16 +75,21 @@ elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'wi
         'PathD2D.cpp',
         'RadialGradientEffectD2D1.cpp',
         'ScaledFontDWrite.cpp',
         'ScaledFontWin.cpp',
         'SourceSurfaceD2D1.cpp',
     ]
     DEFINES['WIN32'] = True
 
+    if CONFIG['_MSC_VER']:
+        # This is intended as a temporary hack to support building with VS2015.
+        # conversion from '*' to '*' requires a narrowing conversion
+        SOURCES['RadialGradientEffectD2D1.cpp'].flags += ['-wd4838']
+
 if CONFIG['MOZ_WIDGET_TOOLKIT'] != 'windows':
     SOURCES += [
         'JobScheduler_posix.cpp',
     ]
 
 if CONFIG['MOZ_ENABLE_SKIA']:
     UNIFIED_SOURCES += [
         'convolver.cpp',

--- a/gfx/thebes/moz.build
+++ b/gfx/thebes/moz.build
@@ -183,16 +183,21 @@ elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'wi
         UNIFIED_SOURCES += [
             'gfxDWriteFontList.cpp',
         ]
         SOURCES += [
             'gfxDWriteCommon.cpp',
             'gfxDWriteFonts.cpp',
         ]
 
+    if CONFIG['_MSC_VER']:
+        # This is intended as a temporary hack to support building with VS2015.
+        # conversion from '*' to '*' requires a narrowing conversion
+        SOURCES['gfxGDIFontList.cpp'].flags += ['-wd4838']
+
 # Are we targeting x86 or x64?  If so, build gfxAlphaRecoverySSE2.cpp.
 if CONFIG['INTEL_ARCHITECTURE']:
     SOURCES += ['gfxAlphaRecoverySSE2.cpp']
     # The file uses SSE2 intrinsics, so it needs special compile flags on some
     # compilers.
     SOURCES['gfxAlphaRecoverySSE2.cpp'].flags += CONFIG['SSE2_FLAGS']
 
 SOURCES += [