diff --git a/lib/compress.js b/lib/compress.js
index ba7c10f4..9185f048 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1009,6 +1009,10 @@ merge(Compressor.prototype, {
                 }
             }
 
+            function get_rvalue(expr) {
+                return expr[expr instanceof AST_Assign ? "right" : "value"];
+            }
+
             function get_lvalues(expr) {
                 var lvalues = Object.create(null);
                 if (expr instanceof AST_Unary) return lvalues;
@@ -1019,7 +1023,7 @@ merge(Compressor.prototype, {
                         lvalues[sym.name] = lvalues[sym.name] || is_lhs(node, tw.parent());
                     }
                 });
-                expr[expr instanceof AST_Assign ? "right" : "value"].walk(tw);
+                get_rvalue(expr).walk(tw);
                 return lvalues;
             }
 
@@ -1044,6 +1048,8 @@ merge(Compressor.prototype, {
                         found = true;
                         if (node instanceof AST_VarDef) {
                             remove(node.name.definition().orig, node.name);
+                            node.value = null;
+                            return node;
                         }
                         return in_list ? MAP.skip : null;
                     }
@@ -1052,16 +1058,13 @@ merge(Compressor.prototype, {
                       case 0: return null;
                       case 1: return node.expressions[0];
                     }
-                    if (node instanceof AST_Definitions && node.definitions.length == 0
-                        || node instanceof AST_SimpleStatement && !node.body) {
-                        return null;
-                    }
+                    if (node instanceof AST_SimpleStatement && !node.body) return null;
                 }));
             }
 
             function value_has_side_effects(expr) {
                 if (expr instanceof AST_Unary) return false;
-                return expr[expr instanceof AST_Assign ? "right" : "value"].has_side_effects(compressor);
+                return get_rvalue(expr).has_side_effects(compressor);
             }
 
             function references_in_scope(def) {
@@ -2303,61 +2306,63 @@ merge(Compressor.prototype, {
         // this scope (not in nested scopes).
         var scope = this;
         var tw = new TreeWalker(function(node, descend){
-            if (node !== self) {
-                if (node instanceof AST_Defun) {
-                    if (!drop_funcs && scope === self) {
-                        var node_def = node.name.definition();
+            if (node === self) return;
+            if (node instanceof AST_Defun) {
+                if (!drop_funcs && scope === self) {
+                    var node_def = node.name.definition();
+                    if (!(node_def.id in in_use_ids)) {
+                        in_use_ids[node_def.id] = true;
+                        in_use.push(node_def);
+                    }
+                }
+                initializations.add(node.name.name, node);
+                return true; // don't go in nested scopes
+            }
+            if (node instanceof AST_SymbolFunarg && scope === self) {
+                var_defs_by_id.add(node.definition().id, node);
+            }
+            if (node instanceof AST_Definitions && scope === self) {
+                node.definitions.forEach(function(def){
+                    var node_def = def.name.definition();
+                    if (def.name instanceof AST_SymbolVar) {
+                        var_defs_by_id.add(node_def.id, def);
+                    }
+                    if (!drop_vars) {
                         if (!(node_def.id in in_use_ids)) {
                             in_use_ids[node_def.id] = true;
                             in_use.push(node_def);
                         }
                     }
-                    initializations.add(node.name.name, node);
-                    return true; // don't go in nested scopes
-                }
-                if (node instanceof AST_Definitions && scope === self) {
-                    node.definitions.forEach(function(def){
-                        var node_def = def.name.definition();
-                        if (def.name instanceof AST_SymbolVar) {
-                            var_defs_by_id.add(node_def.id, def);
+                    if (def.value) {
+                        initializations.add(def.name.name, def.value);
+                        if (def.value.has_side_effects(compressor)) {
+                            def.value.walk(tw);
                         }
-                        if (!drop_vars) {
-                            if (!(node_def.id in in_use_ids)) {
-                                in_use_ids[node_def.id] = true;
-                                in_use.push(node_def);
-                            }
-                        }
-                        if (def.value) {
-                            initializations.add(def.name.name, def.value);
-                            if (def.value.has_side_effects(compressor)) {
-                                def.value.walk(tw);
-                            }
-                        }
-                    });
-                    return true;
-                }
-                var sym;
-                if (scope === self
-                    && (sym = assign_as_unused(node)) instanceof AST_SymbolRef
-                    && self.variables.get(sym.name) === sym.definition()) {
-                    if (node instanceof AST_Assign) node.right.walk(tw);
-                    return true;
-                }
-                if (node instanceof AST_SymbolRef) {
-                    var node_def = node.definition();
-                    if (!(node_def.id in in_use_ids)) {
-                        in_use_ids[node_def.id] = true;
-                        in_use.push(node_def);
                     }
-                    return true;
-                }
-                if (node instanceof AST_Scope) {
-                    var save_scope = scope;
-                    scope = node;
-                    descend();
-                    scope = save_scope;
-                    return true;
+                });
+                return true;
+            }
+            var sym;
+            if (scope === self
+                && (sym = assign_as_unused(node)) instanceof AST_SymbolRef
+                && self.variables.get(sym.name) === sym.definition()) {
+                if (node instanceof AST_Assign) node.right.walk(tw);
+                return true;
+            }
+            if (node instanceof AST_SymbolRef) {
+                var node_def = node.definition();
+                if (!(node_def.id in in_use_ids)) {
+                    in_use_ids[node_def.id] = true;
+                    in_use.push(node_def);
                 }
+                return true;
+            }
+            if (node instanceof AST_Scope) {
+                var save_scope = scope;
+                scope = node;
+                descend();
+                scope = save_scope;
+                return true;
             }
         });
         self.walk(tw);
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index e2c5f1be..b1e89a40 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -1388,6 +1388,7 @@ issue_1605_1: {
     options = {
         collapse_vars: true,
         toplevel: false,
+        unused: true,
     }
     input: {
         function foo(x) {
@@ -1410,6 +1411,7 @@ issue_1605_2: {
     options = {
         collapse_vars: true,
         toplevel: "vars",
+        unused: true,
     }
     input: {
         function foo(x) {
@@ -1537,6 +1539,7 @@ issue_1631_3: {
 var_side_effects_1: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var print = console.log.bind(console);
@@ -1559,6 +1562,7 @@ var_side_effects_1: {
 var_side_effects_2: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var print = console.log.bind(console);
@@ -1584,6 +1588,7 @@ var_side_effects_3: {
         collapse_vars: true,
         pure_getters: true,
         unsafe: true,
+        unused: true,
     }
     input: {
         var print = console.log.bind(console);
@@ -1659,6 +1664,7 @@ iife_2: {
         }(foo);
     }
     expect: {
+        var foo;
         !function(x) {
             console.log(x);
         }(bar());
@@ -1945,6 +1951,7 @@ ref_scope: {
 chained_1: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var a = 2;
@@ -1961,6 +1968,7 @@ chained_1: {
 chained_2: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var a;
@@ -2061,6 +2069,7 @@ inner_lvalues: {
 double_def: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var a = x, a = a && y;
@@ -2075,6 +2084,7 @@ double_def: {
 toplevel_single_reference: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         var a;
@@ -2084,9 +2094,10 @@ toplevel_single_reference: {
         }
     }
     expect: {
-        var a;
-        for (var b in x)
+        for (var b in x) {
+            var a;
             b(a = b);
+        }
     }
 }
 
@@ -2889,6 +2900,7 @@ pure_getters_chain: {
     options = {
         collapse_vars: true,
         pure_getters: true,
+        unused: true,
     }
     input: {
         function o(t, r) {
@@ -2909,6 +2921,7 @@ pure_getters_chain: {
 conditional_1: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         function f(a, b) {
@@ -2933,6 +2946,7 @@ conditional_1: {
 conditional_2: {
     options = {
         collapse_vars: true,
+        unused: true,
     }
     input: {
         function f(a, b) {
diff --git a/test/compress/issue-973.js b/test/compress/issue-973.js
index 30f886a8..fee05dfc 100644
--- a/test/compress/issue-973.js
+++ b/test/compress/issue-973.js
@@ -51,6 +51,7 @@ this_binding_collapse_vars: {
     options = {
         collapse_vars: true,
         toplevel: true,
+        unused: true,
     };
     input: {
         var c = a; c();
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 7714ad5d..1acd902b 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -2131,14 +2131,13 @@ redefine_farg_1: {
     }
     expect: {
         function f(a) {
-            var a;
             return typeof a;
         }
         function g() {
-            return"number";
+            return "number";
         }
         function h(a, b) {
-            var a = b;
+            a = b;
             return typeof a;
         }
         console.log(f([]), g([]), h([]));
@@ -2173,10 +2172,9 @@ redefine_farg_2: {
     }
     expect: {
         console.log(function(a) {
-            var a;
             return typeof a;
         }([]), "number",function(a, b) {
-            var a = b;
+            a = b;
             return typeof a;
         }([]));
     }
@@ -2185,11 +2183,13 @@ redefine_farg_2: {
 
 redefine_farg_3: {
     options = {
+        cascade: true,
         evaluate: true,
         inline: true,
         keep_fargs: false,
-        passes: 3,
+        passes: 2,
         reduce_vars: true,
+        sequences: true,
         side_effects: true,
         toplevel: true,
         unused: true,