diff --git a/tools/gyp/pylib/gyp/generator/msvs.py b/tools/gyp/pylib/gyp/generator/msvs.py
index 8fe9e5af23dd38..ba585b1bfc5a10 100644
--- a/tools/gyp/pylib/gyp/generator/msvs.py
+++ b/tools/gyp/pylib/gyp/generator/msvs.py
@@ -2171,6 +2171,9 @@ def _MapFileToMsBuildSourceType(source, rule_dependencies,
   elif ext == '.asm':
     group = 'masm'
     element = 'MASM'
+  elif ext == '.S':
+    group = 'masm'
+    element = 'MASM'
   elif ext == '.idl':
     group = 'midl'
     element = 'Midl'