diff --git a/Objects/stringlib/codecs.h b/Objects/stringlib/codecs.h
index 63bf648d788..7d55f49a003 100644
--- a/Objects/stringlib/codecs.h
+++ b/Objects/stringlib/codecs.h
@@ -8,9 +8,9 @@
 /* Mask to quickly check whether a C 'long' contains a
    non-ASCII, UTF8-encoded char. */
 #if (SIZEOF_LONG == 8)
-# define ASCII_CHAR_MASK 0x8080808080808080L
+# define ASCII_CHAR_MASK 0x8080808080808080UL
 #elif (SIZEOF_LONG == 4)
-# define ASCII_CHAR_MASK 0x80808080L
+# define ASCII_CHAR_MASK 0x80808080UL
 #else
 # error C 'long' size should be either 4 or 8!
 #endif
diff --git a/Objects/stringlib/find_max_char.h b/Objects/stringlib/find_max_char.h
index 098aeec46a5..9e344a0de95 100644
--- a/Objects/stringlib/find_max_char.h
+++ b/Objects/stringlib/find_max_char.h
@@ -8,9 +8,9 @@
 /* Mask to quickly check whether a C 'long' contains a
    non-ASCII, UTF8-encoded char. */
 #if (SIZEOF_LONG == 8)
-# define UCS1_ASCII_CHAR_MASK 0x8080808080808080L
+# define UCS1_ASCII_CHAR_MASK 0x8080808080808080UL
 #elif (SIZEOF_LONG == 4)
-# define UCS1_ASCII_CHAR_MASK 0x80808080L
+# define UCS1_ASCII_CHAR_MASK 0x80808080UL
 #else
 # error C 'long' size should be either 4 or 8!
 #endif
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 353d2bbf2fa..3e3abfc237e 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -4639,9 +4639,9 @@ PyUnicode_DecodeUTF8(const char *s,
 /* Mask to quickly check whether a C 'long' contains a
    non-ASCII, UTF8-encoded char. */
 #if (SIZEOF_LONG == 8)
-# define ASCII_CHAR_MASK 0x8080808080808080L
+# define ASCII_CHAR_MASK 0x8080808080808080UL
 #elif (SIZEOF_LONG == 4)
-# define ASCII_CHAR_MASK 0x80808080L
+# define ASCII_CHAR_MASK 0x80808080UL
 #else
 # error C 'long' size should be either 4 or 8!
 #endif