diff --git a/promql/parser/lex_test.go b/promql/parser/lex_test.go
index 65e142f45..95f4d978d 100644
--- a/promql/parser/lex_test.go
+++ b/promql/parser/lex_test.go
@@ -340,6 +340,10 @@ var tests = []struct {
 				input:    "bool",
 				expected: []Item{{BOOL, 0, "bool"}},
 			},
+			{
+				input:    "atan2",
+				expected: []Item{{ATAN2, 0, "atan2"}},
+			},
 		},
 	},
 	{