diff --git a/platformio/builder/tools/piomisc.py b/platformio/builder/tools/piomisc.py
index 1fa62f93..8cccb857 100644
--- a/platformio/builder/tools/piomisc.py
+++ b/platformio/builder/tools/piomisc.py
@@ -59,7 +59,8 @@ class InoToCPPConverter(object):
             return result
 
         prototype_names = set(
-            [p['match'].group(3).strip() for p in prototypes])
+            [p['match'].group(3).strip() for p in prototypes
+             if p['path'] == file_path])
         split_pos = prototypes[0]['match'].start()
         for item in prototypes:
             if item['path'] == file_path: