diff --git a/expression/expression.go b/expression/expression.go
index 9b635f4f5f459..2155376730748 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -1165,8 +1165,8 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 			return false
 		case tipb.ScalarFuncSig_JsonUnquoteSig:
 			// TiFlash json_unquote now only supports json string generated by cast(json as string)
-			if child_func, ok := function.GetArgs()[0].(*ScalarFunction); ok {
-				return child_func.Function.PbCode() == tipb.ScalarFuncSig_CastJsonAsString
+			if childFunc, ok := function.GetArgs()[0].(*ScalarFunction); ok {
+				return childFunc.Function.PbCode() == tipb.ScalarFuncSig_CastJsonAsString
 			}
 			return false
 		}