diff --git a/python/ycm/completers/cpp/flags.py b/python/ycm/completers/cpp/flags.py
index 6c2fee1c..b09737de 100644
--- a/python/ycm/completers/cpp/flags.py
+++ b/python/ycm/completers/cpp/flags.py
@@ -200,6 +200,6 @@ def _RemoveUnusedFlags( flags, filename ):
 def _SpecialClangIncludes():
   libclang_dir = os.path.dirname( ycm_core.__file__ )
   path_to_includes = os.path.join( libclang_dir, 'clang_includes' )
-  return [ '-I', path_to_includes ]
+  return [ '-isystem', path_to_includes ]