diff --git a/planner/core/plan_cache_param.go b/planner/core/plan_cache_param.go
index 8671431e6ac42..20b6c78471f72 100644
--- a/planner/core/plan_cache_param.go
+++ b/planner/core/plan_cache_param.go
@@ -88,7 +88,7 @@ func (pr *paramReplacer) Leave(in ast.Node) (out ast.Node, ok bool) {
 }
 
 func (pr *paramReplacer) Reset() {
-	pr.params = nil
+	pr.params = make([]*driver.ValueExpr, 0, 4)
 }
 
 // GetParamSQLFromAST returns the parameterized SQL of this AST.