diff --git a/google/auth/impersonated_credentials.py b/google/auth/impersonated_credentials.py
index 334573428..e2724382a 100644
--- a/google/auth/impersonated_credentials.py
+++ b/google/auth/impersonated_credentials.py
@@ -286,7 +286,7 @@ def _refresh_token(self, request):
             self._source_credentials.token_state == credentials.TokenState.STALE
             or self._source_credentials.token_state == credentials.TokenState.INVALID
         ):
-            self._source_credentials._refresh_token(request)
+            self._source_credentials.refresh(request)
 
         body = {
             "delegates": self._delegates,