diff --git a/lib/compress.js b/lib/compress.js
index a26590a6..5bc633b0 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2554,7 +2554,8 @@ Compressor.prototype.compress = function(node) {
                     && all(iife.args, function(arg) {
                         return !(arg instanceof AST_Spread);
                     })) {
-                    var fn_strict = fn.in_strict_mode() && !fn.parent_scope.resolve(true).in_strict_mode();
+                    var fn_strict = fn.in_strict_mode(compressor)
+                        && !fn.parent_scope.resolve(true).in_strict_mode(compressor);
                     var has_await = is_async(fn) ? function(node) {
                         return node instanceof AST_Symbol && node.name == "await";
                     } : function(node) {
@@ -4124,8 +4125,8 @@ Compressor.prototype.compress = function(node) {
     // in_strict_mode()
     // return true if scope executes in Strict Mode
     (function(def) {
-        def(AST_Class, return_this);
-        def(AST_Scope, function() {
+        def(AST_Class, return_true);
+        def(AST_Scope, function(compressor) {
             var body = this.body;
             for (var i = 0; i < body.length; i++) {
                 var stat = body[i];
@@ -4133,8 +4134,8 @@ Compressor.prototype.compress = function(node) {
                 if (stat.value == "use strict") return true;
             }
             var parent = this.parent_scope;
-            if (!parent) return false;
-            return parent.resolve(true).in_strict_mode();
+            if (!parent) return compressor.option("module");
+            return parent.resolve(true).in_strict_mode(compressor);
         });
     })(function(node, func) {
         node.DEFMETHOD("in_strict_mode", func);
@@ -9941,7 +9942,7 @@ Compressor.prototype.compress = function(node) {
     }
 
     function safe_from_strict_mode(fn, compressor) {
-        return fn.in_strict_mode() || !compressor.has_directive("use strict");
+        return fn.in_strict_mode(compressor) || !compressor.has_directive("use strict");
     }
 
     OPT(AST_Call, function(self, compressor) {
diff --git a/test/compress/functions.js b/test/compress/functions.js
index d73a219b..8c2138bb 100644
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
@@ -8623,3 +8623,26 @@ mixed_mode_inline_4_strict: {
     }
     expect_stdout: "PASS"
 }
+
+module_inline: {
+    options = {
+        inline: true,
+        module: true,
+        reduce_vars: true,
+    }
+    input: {
+        var a = f;
+        function f() {
+            return a;
+        }
+        console.log(f() === a);
+    }
+    expect: {
+        var a = f;
+        function f() {
+            return a;
+        }
+        console.log(a === a);
+    }
+    expect_stdout: "true"
+}