diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index 370f21befbdb66..cc98c3ae69e6c2 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -3333,10 +3333,17 @@ func typecheckas(n *Node) {
 		n.Left = typecheck(n.Left, Erv|Easgn)
 	}
 
-	n.Right = typecheck(n.Right, Erv)
+	// Use Efnstruct so we can emit an "N variables but M values" error
+	// to be consistent with typecheckas2 (#26616).
+	n.Right = typecheck(n.Right, Erv|Efnstruct)
 	checkassign(n, n.Left)
 	if n.Right != nil && n.Right.Type != nil {
-		if n.Left.Type != nil {
+		if n.Right.Type.IsFuncArgStruct() {
+			yyerror("assignment mismatch: 1 variable but %d values", n.Right.Type.NumFields())
+			// Multi-value RHS isn't actually valid for OAS; nil out
+			// to indicate failed typechecking.
+			n.Right.Type = nil
+		} else if n.Left.Type != nil {
 			n.Right = assignconv(n.Right, n.Left.Type, "assignment")
 		}
 	}
diff --git a/test/fixedbugs/issue26616.go b/test/fixedbugs/issue26616.go
new file mode 100644
index 00000000000000..46136dc68f5327
--- /dev/null
+++ b/test/fixedbugs/issue26616.go
@@ -0,0 +1,20 @@
+// errorcheck
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var x int = three() // ERROR "1 variable but 3 values"
+
+func f() {
+	var _ int = three() // ERROR "1 variable but 3 values"
+	var a int = three() // ERROR "1 variable but 3 values"
+	a = three()         // ERROR "1 variable but 3 values"
+	b := three()        // ERROR "1 variable but 3 values"
+
+	_, _ = a, b
+}
+
+func three() (int, int, int)