diff --git a/src/cmd/compile/internal/ir/expr.go b/src/cmd/compile/internal/ir/expr.go
index 5355edc176..02b1733f04 100644
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@@ -906,20 +906,20 @@ FindRHS:
 		base.Fatalf("RHS is nil: %v", defn)
 	}
 
-	if reassigned(n) {
+	if Reassigned(n) {
 		return nil
 	}
 
 	return rhs
 }
 
-// reassigned takes an ONAME node, walks the function in which it is defined, and returns a boolean
-// indicating whether the name has any assignments other than its declaration.
-// The second return value is the first such assignment encountered in the walk, if any. It is mostly
-// useful for -m output documenting the reason for inhibited optimizations.
+// Reassigned takes an ONAME node, walks the function in which it is
+// defined, and returns a boolean indicating whether the name has any
+// assignments other than its declaration.
 // NB: global variables are always considered to be re-assigned.
-// TODO: handle initial declaration not including an assignment and followed by a single assignment?
-func reassigned(name *Name) bool {
+// TODO: handle initial declaration not including an assignment and
+// followed by a single assignment?
+func Reassigned(name *Name) bool {
 	if name.Op() != ONAME {
 		base.Fatalf("reassigned %v", name)
 	}
@@ -934,7 +934,10 @@ func reassigned(name *Name) bool {
 
 	// isName reports whether n is a reference to name.
 	isName := func(x Node) bool {
-		n, ok := x.(*Name)
+		if x == nil {
+			return false
+		}
+		n, ok := OuterValue(x).(*Name)
 		return ok && n.Canonical() == name
 	}
 
@@ -953,9 +956,14 @@ func reassigned(name *Name) bool {
 					return true
 				}
 			}
+		case OASOP:
+			n := n.(*AssignOpStmt)
+			if isName(n.X) {
+				return true
+			}
 		case OADDR:
 			n := n.(*AddrExpr)
-			if isName(OuterValue(n.X)) {
+			if isName(n.X) {
 				return true
 			}
 		case ORANGE: