diff --git a/lib/filesystem.js b/lib/filesystem.js
index 908b0dd..ce10245 100644
--- a/lib/filesystem.js
+++ b/lib/filesystem.js
@@ -14,7 +14,7 @@ const pipeline = promisify(stream.pipeline)
 class Filesystem {
   constructor (src) {
     this.src = path.resolve(src)
-    this.header = { files: {} }
+    this.header = { files: Object.create(null) }
     this.offset = BigInt(0)
   }
 
@@ -24,7 +24,7 @@ class Filesystem {
     for (const dir of dirs) {
       if (dir !== '.') {
         if (!json.files[dir]) {
-          json.files[dir] = { files: {} }
+          json.files[dir] = { files: Object.create(null) }
         }
         json = json.files[dir]
       }
@@ -38,10 +38,10 @@ class Filesystem {
     const name = path.basename(p)
     const node = this.searchNodeFromDirectory(path.dirname(p))
     if (node.files == null) {
-      node.files = {}
+      node.files = Object.create(null)
     }
     if (node.files[name] == null) {
-      node.files[name] = {}
+      node.files[name] = Object.create(null)
     }
     return node.files[name]
   }
@@ -51,7 +51,7 @@ class Filesystem {
     if (shouldUnpack) {
       node.unpacked = shouldUnpack
     }
-    node.files = node.files || {}
+    node.files = node.files || Object.create(null)
     return node.files
   }
 
diff --git a/test/api-spec.js b/test/api-spec.js
index 3d4f5ce..d50323d 100644
--- a/test/api-spec.js
+++ b/test/api-spec.js
@@ -94,4 +94,12 @@ describe('api', function () {
     const expected = await fs.readFile('test/input/packthis-unicode-path/dir1/女の子.txt', 'utf8')
     return compFileLists(actual, expected)
   })
+  it('should create files/directories whose names are properties of Object.prototype', async () => {
+    await asar.createPackage('test/input/packthis-object-prototype/', 'tmp/packthis-object-prototype.asar')
+    return compFiles('tmp/packthis-object-prototype.asar', 'test/expected/packthis-object-prototype.asar')
+  })
+  it('should extract files/directories whose names are properties of Object.prototype', () => {
+    asar.extractAll('test/expected/packthis-object-prototype.asar', 'tmp/packthis-object-prototype/')
+    return compDirs('test/input/packthis-object-prototype/', 'tmp/packthis-object-prototype')
+  })
 })
diff --git a/test/expected/packthis-object-prototype.asar b/test/expected/packthis-object-prototype.asar
new file mode 100644
index 0000000..a7bad8c
Binary files /dev/null and b/test/expected/packthis-object-prototype.asar differ
diff --git a/test/input/packthis-object-prototype/__proto__ b/test/input/packthis-object-prototype/__proto__
new file mode 100644
index 0000000..84437e7
--- /dev/null
+++ b/test/input/packthis-object-prototype/__proto__
@@ -0,0 +1 @@
+__proto__
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/constructor/__proto__ b/test/input/packthis-object-prototype/constructor/__proto__
new file mode 100644
index 0000000..bd07bcf
--- /dev/null
+++ b/test/input/packthis-object-prototype/constructor/__proto__
@@ -0,0 +1 @@
+constructor/__proto__
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/constructor/constructor b/test/input/packthis-object-prototype/constructor/constructor
new file mode 100644
index 0000000..4c4cc0c
--- /dev/null
+++ b/test/input/packthis-object-prototype/constructor/constructor
@@ -0,0 +1 @@
+constructor/constructor
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/constructor/file1 b/test/input/packthis-object-prototype/constructor/file1
new file mode 100644
index 0000000..7d188b0
--- /dev/null
+++ b/test/input/packthis-object-prototype/constructor/file1
@@ -0,0 +1 @@
+constructor/file1
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/file1 b/test/input/packthis-object-prototype/file1
new file mode 100644
index 0000000..08219db
--- /dev/null
+++ b/test/input/packthis-object-prototype/file1
@@ -0,0 +1 @@
+file1
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/file2 b/test/input/packthis-object-prototype/file2
new file mode 100644
index 0000000..30d67d4
--- /dev/null
+++ b/test/input/packthis-object-prototype/file2
@@ -0,0 +1 @@
+file2
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/__proto__ b/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/__proto__
new file mode 100644
index 0000000..1cd727b
--- /dev/null
+++ b/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/__proto__
@@ -0,0 +1 @@
+folder1/constructor/constructor/__proto__/__proto__
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/file1 b/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/file1
new file mode 100644
index 0000000..c9cb751
--- /dev/null
+++ b/test/input/packthis-object-prototype/folder1/constructor/constructor/__proto__/file1
@@ -0,0 +1 @@
+folder1/constructor/constructor/__proto__/file1
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/folder1/constructor/constructor/constructor b/test/input/packthis-object-prototype/folder1/constructor/constructor/constructor
new file mode 100644
index 0000000..757c3ea
--- /dev/null
+++ b/test/input/packthis-object-prototype/folder1/constructor/constructor/constructor
@@ -0,0 +1 @@
+folder1/constructor/constructor/constructor
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/folder1/constructor/constructor/file1 b/test/input/packthis-object-prototype/folder1/constructor/constructor/file1
new file mode 100644
index 0000000..3b0d002
--- /dev/null
+++ b/test/input/packthis-object-prototype/folder1/constructor/constructor/file1
@@ -0,0 +1 @@
+folder1/constructor/constructor/file1
\ No newline at end of file
diff --git a/test/input/packthis-object-prototype/folder1/file1 b/test/input/packthis-object-prototype/folder1/file1
new file mode 100644
index 0000000..b3ce553
--- /dev/null
+++ b/test/input/packthis-object-prototype/folder1/file1
@@ -0,0 +1 @@
+folder1/file1
\ No newline at end of file