diff --git a/promql/parser/parse.go b/promql/parser/parse.go
index 79424dd98..6e9bbe23a 100644
--- a/promql/parser/parse.go
+++ b/promql/parser/parse.go
@@ -169,6 +169,7 @@ func newParser(input string) *parser {
 
 	p.injecting = false
 	p.parseErrors = nil
+	p.generatedParserResult = nil
 
 	// Clear lexer struct before reusing.
 	p.lex = Lexer{