1 files changed, 1 insertions, 1 deletions
diff --git a/lib/compress.js b/lib/compress.js
index 2b61e91c..a8bf0d9d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4196,7 +4196,7 @@ merge(Compressor.prototype, {
             var left = this.left;
             if (left instanceof AST_PropAccess) {
                 var expr = left.expression;
-                if (expr instanceof AST_Assign && !expr.may_throw_on_access(compressor)) {
+                if (expr instanceof AST_Assign && expr.operator == "=" && !expr.may_throw_on_access(compressor)) {
                     expr.write_only = "p";
                 }
                 if (compressor.has_directive("use strict") && expr.is_constant()) return this;