diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index c76b9a3..9e72042 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -84,6 +84,7 @@
     # build.
     'USE_HEADERMAP' => 'NO',
     'ALWAYS_SEARCH_USER_PATHS' => 'NO',
+    'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
   }
 
   s.default_subspecs = 'Interface', 'Implementation'
diff --git a/templates/gRPC-Core.podspec.template b/templates/gRPC-Core.podspec.template
index 6077f80..e34bc83 100644
--- a/templates/gRPC-Core.podspec.template
+++ b/templates/gRPC-Core.podspec.template
@@ -111,6 +111,7 @@
       # build.
       'USE_HEADERMAP' => 'NO',
       'ALWAYS_SEARCH_USER_PATHS' => 'NO',
+      'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
     }
 
     s.default_subspecs = 'Interface', 'Implementation'