diff --git a/src/rpc/src/rpcMain.c b/src/rpc/src/rpcMain.c
index acceaf9d7a63f3378afbc8d8f485f14f77b50af6..4ccdec2bc718aa3f35aa2e63373df103f1d34f18 100644
--- a/src/rpc/src/rpcMain.c
+++ b/src/rpc/src/rpcMain.c
@@ -630,7 +630,14 @@ static void rpcReleaseConn(SRpcConn *pConn) {
   } else {
     // if there is an outgoing message, free it
     if (pConn->outType && pConn->pReqMsg) {
-      if (pConn->pContext) pConn->pContext->pConn = NULL; 
+      if (pContext->pRsp) {   
+        // for synchronous API, post semaphore to unblock app
+        pContext->pRsp->code = TSDB_CODE_RPC_APP_ERROR;
+        pContext->pRsp->pCont = NULL;
+        pContext->pRsp->contLen = 0;
+        tsem_post(pContext->pSem);
+      }
+      pConn->pContext->pConn = NULL; 
       taosRemoveRef(tsRpcRefId, pConn->pContext->rid);
     }
   }