Index: Modules/_pickle.c
===================================================================
--- Modules/_pickle.c	(revision 64162)
+++ Modules/_pickle.c	(working copy)
@@ -2694,24 +2694,24 @@
  * of x-platform bugs.
  */
 static long
-calc_binint(char *s, int size)
+calc_binint(char *bytes, int size)
 {
-    unsigned char c;
-    int i;
-    long x = 0L;
+    unsigned char *s = (unsigned char *)bytes;
+    int i = size;
+    long x = 0;
 
     for (i = 0; i < size; i++) {
-        c = (unsigned char)s[i];
-        x |= (long)c << (i * 8);
+        x |= (long)s[i] << (i * 8);
     }
-#if SIZEOF_LONG > 4
+
     /* Unlike BININT1 and BININT2, BININT (more accurately BININT4)
      * is signed, so on a box with longs bigger than 4 bytes we need
      * to extend a BININT's sign bit to the full width.
      */
-    if (x == 4 && x & (1L << 31))
-        x |= (~0L) << 32;
-#endif
+    if (SIZEOF_LONG > 4 && size == 4) {
+        x |= -(x & (1L << 31));
+    }
+
     return x;
 }