diff --git a/lib/compress.js b/lib/compress.js
index 3309d7fa61..342748a087 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -10462,9 +10462,11 @@ Compressor.prototype.compress = function(node) {
                         def.orig[def.orig.indexOf(node)] = name;
                         for (var s = scope; s !== def.scope && (s = s.parent_scope);) {
                             remove(s.enclosed, def);
+                            s._var_names = undefined;
                         }
-                        def.scope = scope;
+                        def.scope.variables.del(def.name);
                         scope.variables.set(def.name, def);
+                        def.scope = scope;
                     }),
                     value: defn.value,
                 });
diff --git a/test/compress/let.js b/test/compress/let.js
index 7205090cec..ec5c130e5f 100644
--- a/test/compress/let.js
+++ b/test/compress/let.js
@@ -2566,3 +2566,35 @@ issue_5787: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_5950: {
+    options = {
+        conditionals: true,
+        join_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        {
+            let a;
+            if (console.log("PASS")) {
+                var b = function() {
+                    a;
+                }, c = b;
+            }
+        }
+    }
+    expect: {
+        "use strict";
+        {
+            let a;
+            console.log("PASS") && function() {
+                a;
+            };
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}