diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 0a7ddd4..7a2dd0c 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -38,7 +38,7 @@
         try:
             try:
                 import marshal
-                marshal.loads('')
+                marshal.loads(b'')
             except EOFError:
                 pass
         finally:
diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
index 9a25012..96a70ec 100644
--- a/Lib/test/test_marshal.py
+++ b/Lib/test/test_marshal.py
@@ -184,7 +184,7 @@
                 pass
 
     def test_loads_recursion(self):
-        s = 'c' + ('X' * 4*4) + '{' * 2**20
+        s = b'c' + (b'X' * 4*4) + b'{' * 2**20
         self.assertRaises(ValueError, marshal.loads, s)
 
     def test_recursion_limit(self):
@@ -257,6 +257,11 @@
             finally:
                 support.unlink(support.TESTFN)
 
+    def test_loads_reject_unicode_strings(self):
+        # Issue #14177: marshal.loads() should not accept unicode strings
+        unicode_string = 'T'
+        self.assertRaises(TypeError, marshal.loads, unicode_string)
+
 
 def test_main():
     support.run_unittest(IntTestCase,