Index: Modules/_pickle.c
===================================================================
--- Modules/_pickle.c	(revision 76876)
+++ Modules/_pickle.c	(working copy)
@@ -3729,7 +3729,7 @@
      */
     if (self->num_marks > 0 && self->marks[self->num_marks - 1] == len) {
         self->num_marks--;
-    } else if (len >= 0) {
+    } else if (len > 0) {
         len--;
         Py_DECREF(self->stack->data[len]);
         self->stack->length = len;
Index: Lib/test/pickletester.py
===================================================================
--- Lib/test/pickletester.py	(revision 76876)
+++ Lib/test/pickletester.py	(working copy)
@@ -1139,6 +1139,9 @@
         # Test issue4298
         s = bytes([0x58, 0, 0, 0, 0x54])
         self.assertRaises(EOFError, pickle.loads, s)
+        # Test issue7455
+        s = b'0'
+        self.assertRaises(pickle.UnpicklingError, pickle.loads, s)
 
 
 class AbstractPersistentPicklerTests(unittest.TestCase):