diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 97f40815b87b4..4514134979666 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -391,7 +391,7 @@ def download_stage0(self):
 
         if self.rustc().startswith(self.bin_root()) and \
                 (not os.path.exists(self.rustc()) or
-                 self.program_out_of_date(self.rustc_stamp())):
+                 self.program_out_of_date(self.rustc_stamp(), self.date)):
             if os.path.exists(self.bin_root()):
                 shutil.rmtree(self.bin_root())
             tarball_suffix = '.tar.xz' if support_xz() else '.tar.gz'
@@ -427,7 +427,7 @@ def download_stage0(self):
                 self.fix_bin_or_dylib("{}/bin/rustfmt".format(self.bin_root()))
                 self.fix_bin_or_dylib("{}/bin/cargo-fmt".format(self.bin_root()))
                 with output(self.rustfmt_stamp()) as rustfmt_stamp:
-                    rustfmt_stamp.write(self.date + self.rustfmt_channel)
+                    rustfmt_stamp.write(self.rustfmt_channel)
 
         if self.downloading_llvm():
             # We want the most recent LLVM submodule update to avoid downloading
@@ -454,7 +454,7 @@ def download_stage0(self):
                 for binary in ["llvm-config", "FileCheck"]:
                     self.fix_bin_or_dylib("{}/bin/{}".format(self.llvm_root(), binary))
                 with output(self.llvm_stamp()) as llvm_stamp:
-                    llvm_stamp.write(self.date + llvm_sha + str(llvm_assertions))
+                    llvm_stamp.write(llvm_sha + str(llvm_assertions))
 
     def downloading_llvm(self):
         opt = self.get_toml('download-ci-llvm', 'llvm')
@@ -616,12 +616,12 @@ def llvm_stamp(self):
         return os.path.join(self.llvm_root(), '.llvm-stamp')
 
 
-    def program_out_of_date(self, stamp_path, extra=""):
+    def program_out_of_date(self, stamp_path, key):
         """Check if the given program stamp is out of date"""
         if not os.path.exists(stamp_path) or self.clean:
             return True
         with open(stamp_path, 'r') as stamp:
-            return (self.date + extra) != stamp.read()
+            return key != stamp.read()
 
     def bin_root(self):
         """Return the binary root directory
diff --git a/src/bootstrap/bootstrap_test.py b/src/bootstrap/bootstrap_test.py
index 0e941e1367668..615071141594f 100644
--- a/src/bootstrap/bootstrap_test.py
+++ b/src/bootstrap/bootstrap_test.py
@@ -70,6 +70,7 @@ def setUp(self):
         self.build.build_dir = self.container
         self.rustc_stamp_path = os.path.join(self.container, "stage0",
                                              ".rustc-stamp")
+        self.key = self.build.date + str(None)
 
     def tearDown(self):
         rmtree(self.container)
@@ -78,19 +79,19 @@ def test_stamp_path_does_not_exists(self):
         """Return True when the stamp file does not exists"""
         if os.path.exists(self.rustc_stamp_path):
             os.unlink(self.rustc_stamp_path)
-        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path))
+        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
     def test_dates_are_different(self):
         """Return True when the dates are different"""
         with open(self.rustc_stamp_path, "w") as rustc_stamp:
-            rustc_stamp.write("2017-06-14")
-        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path))
+            rustc_stamp.write("2017-06-14None")
+        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
     def test_same_dates(self):
         """Return False both dates match"""
         with open(self.rustc_stamp_path, "w") as rustc_stamp:
-            rustc_stamp.write("2017-06-15")
-        self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path))
+            rustc_stamp.write("2017-06-15None")
+        self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
 
 if __name__ == '__main__':