diff --git a/lib/compress.js b/lib/compress.js
index b06186ee..b5c67c2d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -12560,7 +12560,8 @@ Compressor.prototype.compress = function(node) {
         var found = false;
         var generated = false;
         var keep_duplicate = compressor.has_directive("use strict");
-        var keys = new Dictionary();
+        var keys = [];
+        var map = new Dictionary();
         var values = [];
         self.properties.forEach(function(prop) {
             if (!(prop instanceof AST_Spread)) return process(prop);
@@ -12603,19 +12604,27 @@ Compressor.prototype.compress = function(node) {
         return make_node(AST_Object, self, { properties: values });
 
         function flush() {
-            keys.each(function(props) {
-                if (props.length == 1) return values.push(props[0]);
+            keys.forEach(function(key) {
+                var props = map.get(key);
+                switch (props.length) {
+                  case 0:
+                    return;
+                  case 1:
+                    return values.push(props[0]);
+                }
                 changed = true;
                 var tail = keep_duplicate && !generated && props.pop();
                 values.push(props.length == 1 ? props[0] : make_node(AST_ObjectKeyVal, self, {
                     key: props[0].key,
                     value: make_sequence(self, props.map(function(prop) {
                         return prop.value;
-                    }))
+                    })),
                 }));
                 if (tail) values.push(tail);
+                props.length = 0;
             });
-            keys = new Dictionary();
+            keys = [];
+            map = new Dictionary();
         }
 
         function process(prop) {
@@ -12631,14 +12640,15 @@ Compressor.prototype.compress = function(node) {
             }
             if (can_hoist_property(prop)) {
                 if (prop.value.has_side_effects(compressor)) flush();
-                keys.add(key, prop);
+                keys.push(key);
+                map.add(key, prop);
             } else {
                 flush();
                 values.push(prop);
             }
             if (found && !generated && typeof key == "string" && RE_POSITIVE_INTEGER.test(key)) {
                 generated = true;
-                if (keys.has(key)) prop = keys.get(key)[0];
+                if (map.has(key)) prop = map.get(key)[0];
                 prop.key = make_node(AST_Number, prop, { value: +key });
             }
         }
diff --git a/test/compress/objects.js b/test/compress/objects.js
index beec4bfd..3e110fe0 100644
--- a/test/compress/objects.js
+++ b/test/compress/objects.js
@@ -198,9 +198,9 @@ numeric_literal: {
     expect_exact: [
         'var obj = {',
         '    0: 0,',
-        '    37: 4,',
-        '    42: 3,',
         '    "-0": 1,',
+        '    42: 3,',
+        '    37: 4,',
         '    o: 5,',
         '    1e42: 8,',
         '    b: 7',
@@ -521,3 +521,25 @@ issue_4415: {
     expect_stdout: "PASS"
     node_version: ">=4"
 }
+
+issue_5213: {
+    options = {
+        objects: true,
+    }
+    input: {
+        var a = "FAIL";
+        console.log({
+            p: a = "PASS",
+            0: a,
+            p: null,
+        }[0]);
+    }
+    expect: {
+        var a = "FAIL";
+        console.log({
+            p: (a = "PASS", null),
+            0: a,
+        }[0]);
+    }
+    expect_stdout: "PASS"
+}
diff --git a/test/sandbox.js b/test/sandbox.js
index 8ebbaab7..bc02114f 100644
--- a/test/sandbox.js
+++ b/test/sandbox.js
@@ -252,7 +252,7 @@ function run_code_vm(code, toplevel, timeout) {
         var ctx = vm.createContext({ console: console });
         // for Node.js v6
         vm.runInContext(setup_code, ctx);
-        vm.runInContext(toplevel ? "(function(){" + code + "})();" : code, ctx, { timeout: timeout });
+        vm.runInContext(toplevel ? "(function(){\n" + code + "\n})();" : code, ctx, { timeout: timeout });
         // for Node.js v4
         return strip_color_codes(stdout.replace(/\b(Array \[|Object {)/g, function(match) {
             return match.slice(-1);
@@ -266,7 +266,7 @@ function run_code_vm(code, toplevel, timeout) {
 
 function run_code_exec(code, toplevel, timeout) {
     if (toplevel) {
-        code = setup_code + "(function(){" + code + "})();";
+        code = setup_code + "(function(){\n" + code + "\n})();";
     } else {
         code = code.replace(/^((["'])[^"']*\2(;|$))?/, function(directive) {
             return directive + setup_code;