diff --git a/lib/storage/file.js b/lib/storage/file.js
index e3bc507e986..bd288e29df4 100644
--- a/lib/storage/file.js
+++ b/lib/storage/file.js
@@ -24,6 +24,7 @@ var concat = require('concat-stream');
 var createErrorClass = require('create-error-class');
 var crypto = require('crypto');
 var duplexify = require('duplexify');
+var extend = require('extend');
 var format = require('string-format-obj');
 var fs = require('fs');
 var hashStreamValidation = require('hash-stream-validation');
@@ -979,6 +980,8 @@ File.prototype.getSignedPolicy = function(options, callback) {
     throw new Error('An expiration date cannot be in the past.');
   }
 
+  options = extend({}, options);
+
   var conditions = [
     ['eq', '$key', this.name],
     {
@@ -1159,6 +1162,8 @@ File.prototype.getSignedUrl = function(options, callback) {
     throw new Error('An expiration date cannot be in the past.');
   }
 
+  options = extend({}, options);
+
   options.action = {
     read: 'GET',
     write: 'PUT',
diff --git a/test/storage/file.js b/test/storage/file.js
index 0e8229a7d85..10d1f91a7ba 100644
--- a/test/storage/file.js
+++ b/test/storage/file.js
@@ -1353,6 +1353,20 @@ describe('File', function() {
       });
     });
 
+    it('should not modify the configuration object', function(done) {
+      var config = {
+        expires: Date.now() + 5
+      };
+
+      var originalConfig = extend({}, config);
+
+      file.getSignedPolicy(config, function(err) {
+        assert.ifError(err);
+        assert.deepEqual(config, originalConfig);
+        done();
+      });
+    });
+
     it('should return an error if getCredentials errors', function(done) {
       var error = new Error('Error.');
 
@@ -1642,6 +1656,21 @@ describe('File', function() {
       });
     });
 
+    it('should not modify the configuration object', function(done) {
+      var config = {
+        action: 'read',
+        expires: Date.now() + 5
+      };
+
+      var originalConfig = extend({}, config);
+
+      file.getSignedUrl(config, function(err) {
+        assert.ifError(err);
+        assert.deepEqual(config, originalConfig);
+        done();
+      });
+    });
+
     it('should return an error if getCredentials errors', function(done) {
       var error = new Error('Error.');