diff --git a/promql/ast.go b/promql/ast.go
index 249eab4fa..dba38db3b 100644
--- a/promql/ast.go
+++ b/promql/ast.go
@@ -306,11 +306,11 @@ func Walk(v Visitor, node Node, path []Node) error {
 type inspector func(Node, []Node) error
 
 func (f inspector) Visit(node Node, path []Node) (Visitor, error) {
-	if err := f(node, path); err == nil {
-		return f, nil
-	} else {
+	if err := f(node, path); err != nil {
 		return nil, err
 	}
+
+	return f, nil
 }
 
 // Inspect traverses an AST in depth-first order: It starts by calling
diff --git a/promql/engine.go b/promql/engine.go
index 2bf8705cb..e6e532248 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -614,7 +614,7 @@ func extractFuncFromPath(p []Node) string {
 	return extractFuncFromPath(p[:len(p)-1])
 }
 
-func checkForSeriesSetExpansion(expr Expr, ctx context.Context) error {
+func checkForSeriesSetExpansion(ctx context.Context, expr Expr) error {
 	switch e := expr.(type) {
 	case *MatrixSelector:
 		if e.series == nil {
@@ -966,7 +966,7 @@ func (ev *evaluator) eval(expr Expr) Value {
 		}
 
 		sel := e.Args[matrixArgIndex].(*MatrixSelector)
-		if err := checkForSeriesSetExpansion(sel, ev.ctx); err != nil {
+		if err := checkForSeriesSetExpansion(ev.ctx, sel); err != nil {
 			ev.error(err)
 		}
 		mat := make(Matrix, 0, len(sel.series)) // Output matrix.
@@ -1100,7 +1100,7 @@ func (ev *evaluator) eval(expr Expr) Value {
 		})
 
 	case *VectorSelector:
-		if err := checkForSeriesSetExpansion(e, ev.ctx); err != nil {
+		if err := checkForSeriesSetExpansion(ev.ctx, e); err != nil {
 			ev.error(err)
 		}
 		mat := make(Matrix, 0, len(e.series))
@@ -1175,7 +1175,7 @@ func durationToInt64Millis(d time.Duration) int64 {
 
 // vectorSelector evaluates a *VectorSelector expression.
 func (ev *evaluator) vectorSelector(node *VectorSelector, ts int64) Vector {
-	if err := checkForSeriesSetExpansion(node, ev.ctx); err != nil {
+	if err := checkForSeriesSetExpansion(ev.ctx, node); err != nil {
 		ev.error(err)
 	}
 
@@ -1249,7 +1249,7 @@ func putPointSlice(p []Point) {
 
 // matrixSelector evaluates a *MatrixSelector expression.
 func (ev *evaluator) matrixSelector(node *MatrixSelector) Matrix {
-	if err := checkForSeriesSetExpansion(node, ev.ctx); err != nil {
+	if err := checkForSeriesSetExpansion(ev.ctx, node); err != nil {
 		ev.error(err)
 	}
 
diff --git a/promql/test.go b/promql/test.go
index 4dfd4b245..2bd083495 100644
--- a/promql/test.go
+++ b/promql/test.go
@@ -606,9 +606,9 @@ func (ll *LazyLoader) parse(input string) error {
 			}
 			ll.loadCmd = cmd
 			return nil
-		} else {
-			return raise(i, "invalid command %q", l)
 		}
+
+		return raise(i, "invalid command %q", l)
 	}
 	return errors.New("no \"load\" command found")
 }