diff --git a/lib/compress.js b/lib/compress.js
index 87e0f964..9320d5a7 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -12898,8 +12898,8 @@ Compressor.prototype.compress = function(node) {
                     return cond.negate(compressor);
                   case "??":
                     return make_node(AST_Binary, self, {
-                        operator: "===",
-                        left: make_node(AST_Undefined, self).transform(compressor),
+                        operator: "==",
+                        left: make_node(AST_Null, self),
                         right: cond,
                     });
                 }
diff --git a/test/compress/nullish.js b/test/compress/nullish.js
index be9c752d..b141d10b 100644
--- a/test/compress/nullish.js
+++ b/test/compress/nullish.js
@@ -274,7 +274,7 @@ inline_binary_nullish: {
         })();
     }
     expect: {
-        if (void 0 === function() {
+        if (null == function() {
             while (console.log("foo"));
         }())
             while (console.log("bar"));
@@ -304,3 +304,42 @@ issue_4679: {
     expect_stdout: "PASS"
     node_version: ">=14"
 }
+
+issue_5266: {
+    options = {
+        inline: true,
+    }
+    input: {
+        [
+            42,
+            null,
+            false,
+            void 0,
+            "FAIL",
+        ].forEach(function (a) {
+            a ?? function() {
+                while (console.log(a));
+            }();
+        });
+    }
+    expect: {
+        [
+            42,
+            null,
+            false,
+            void 0,
+            "FAIL",
+        ].forEach(function (a) {
+            if (null == a) {
+                while (console.log(a));
+                return;
+            } else
+                return;
+        });
+    }
+    expect_stdout: [
+        "null",
+        "undefined",
+    ]
+    node_version: ">=14"
+}