diff --git a/lib/compress.js b/lib/compress.js
index 7d67906b..fd59fb32 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2720,6 +2720,7 @@ merge(Compressor.prototype, {
         };
         var in_use = [];
         var in_use_ids = Object.create(null); // avoid expensive linear scans of in_use
+        var fixed_ids = Object.create(null);
         if (self instanceof AST_Toplevel && compressor.top_retain) {
             self.variables.each(function(def) {
                 if (compressor.top_retain(def) && !(def.id in in_use_ids)) {
@@ -2730,7 +2731,6 @@ merge(Compressor.prototype, {
         }
         var var_defs_by_id = new Dictionary();
         var initializations = new Dictionary();
-        var fixed_values = Object.create(null);
         // pass 1: find out which symbols are directly used in
         // this scope (not in nested scopes).
         var scope = this;
@@ -2767,9 +2767,8 @@ merge(Compressor.prototype, {
                         if (def.value.has_side_effects(compressor)) {
                             def.value.walk(tw);
                         }
-                        var fixed = def.name.fixed_value();
-                        if (fixed === def.value) {
-                            fixed_values[node_def.id] = fixed;
+                        if (def.name.fixed_value() === def.value) {
+                            fixed_ids[node_def.id] = true;
                         }
                     }
                 });
@@ -2799,8 +2798,8 @@ merge(Compressor.prototype, {
                         var in_use = def.id in in_use_ids;
                         if (node instanceof AST_Assign) {
                             if (!in_use
-                                || def.id in fixed_values
-                                    && fixed_values[def.id] !== node.right) {
+                                || def.id in fixed_ids
+                                    && node.left.fixed_value() !== node.right) {
                                 return maintain_this_binding(parent, node, node.right.transform(tt));
                             }
                         } else if (!in_use) return make_node(AST_Number, node, {
@@ -2870,7 +2869,7 @@ merge(Compressor.prototype, {
                                     return;
                                 }
                             }
-                            if (def.value && sym.id in fixed_values && fixed_values[sym.id] !== def.value) {
+                            if (def.value && sym.id in fixed_ids && def.name.fixed_value() !== def.value) {
                                 def.value = def.value.drop_side_effect_free(compressor);
                             }
                             if (def.value) {
@@ -2982,9 +2981,8 @@ merge(Compressor.prototype, {
                 && self.variables.get(sym.name) === (node_def = sym.definition())) {
                 if (node instanceof AST_Assign) {
                     node.right.walk(tw);
-                    var fixed = node.left.fixed_value();
-                    if (fixed === node.right) {
-                        fixed_values[node_def.id] = fixed;
+                    if (node.left.fixed_value() === node.right) {
+                        fixed_ids[node_def.id] = true;
                     }
                 }
                 return true;
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index 48958e2b..5ad489b9 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -1627,3 +1627,20 @@ double_assign_3: {
         var a;
     }
 }
+
+cascade_drop_assign: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var a, b = a = "PASS";
+        console.log(b);
+    }
+    expect: {
+        var b = "PASS";
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+}