diff --git a/promql/test.go b/promql/test.go
index 024725df2..26a9a4169 100644
--- a/promql/test.go
+++ b/promql/test.go
@@ -425,7 +425,7 @@ func (t *Test) Run() error {
 	return nil
 }
 
-// exec processes a single step of the test
+// exec processes a single step of the test.
 func (t *Test) exec(tc testCommand) error {
 	switch cmd := tc.(type) {
 	case *clearCmd: