diff --git a/client/client.gyp b/client/client.gyp
index 9892fb6c..45ae382a 100644
--- a/client/client.gyp
+++ b/client/client.gyp
@@ -61,6 +61,11 @@
             ],
           },
         }],
+        ['OS!="mac"', {
+          'sources!': [
+            'capture_context_mac.S',
+          ],
+        }],
       ],
       'direct_dependent_settings': {
         'include_dirs': [
diff --git a/util/util.gyp b/util/util.gyp
index 9321ab8d..8269bd42 100644
--- a/util/util.gyp
+++ b/util/util.gyp
@@ -284,6 +284,10 @@
               },
             }],
           ],
+        }, {  # else: OS!="win"
+          'sources!': [
+            'win/capture_context.asm',
+          ],
         }],
       ],
     },