diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
index 53772246eb8..9237af0b638 100644
--- a/Lib/test/test_marshal.py
+++ b/Lib/test/test_marshal.py
@@ -39,3 +39,6 @@ def to_little_endian_string(value, nbytes):
             base = 0
         else:
             base >>= 1
+
+# Simple-minded check for SF 588452: Debug build crashes
+marshal.dumps([128] * 1000)
diff --git a/Python/marshal.c b/Python/marshal.c
index 0df46cf1636..c00586dc932 100644
--- a/Python/marshal.c
+++ b/Python/marshal.c
@@ -84,17 +84,17 @@ w_string(char *s, int n, WFILE *p)
 static void
 w_short(int x, WFILE *p)
 {
-	w_byte( x      & 0xff, p);
-	w_byte((x>> 8) & 0xff, p);
+	w_byte((char)( x      & 0xff), p);
+	w_byte((char)((x>> 8) & 0xff), p);
 }
 
 static void
 w_long(long x, WFILE *p)
 {
-	w_byte((int)( x      & 0xff), p);
-	w_byte((int)((x>> 8) & 0xff), p);
-	w_byte((int)((x>>16) & 0xff), p);
-	w_byte((int)((x>>24) & 0xff), p);
+ 	w_byte((char)( x      & 0xff), p);
+ 	w_byte((char)((x>> 8) & 0xff), p);
+ 	w_byte((char)((x>>16) & 0xff), p);
+ 	w_byte((char)((x>>24) & 0xff), p);
 }
 
 #if SIZEOF_LONG > 4