diff --git a/crypto/hmac/hmac_lcl.h b/crypto/hmac/hmac_lcl.h
index b95c8673f9a5daa85d5301c1ddbb623e95f47279..f93e61fd745c4c5a6236f25de011d5943d7b192e 100644
--- a/crypto/hmac/hmac_lcl.h
+++ b/crypto/hmac/hmac_lcl.h
@@ -73,4 +73,8 @@ struct hmac_ctx_st {
     unsigned char key[HMAC_MAX_MD_CBLOCK];
 };
 
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
 #endif