diff --git a/Objects/stringlib/codecs.h b/Objects/stringlib/codecs.h
index 197605b..b6ca404 100644
--- a/Objects/stringlib/codecs.h
+++ b/Objects/stringlib/codecs.h
@@ -6,14 +6,14 @@
 
 #include "pycore_bitutils.h"      // _Py_bswap32()
 
-/* Mask to quickly check whether a C 'long' contains a
+/* Mask to quickly check whether a C 'size_t' contains a
    non-ASCII, UTF8-encoded char. */
-#if (SIZEOF_LONG == 8)
-# define ASCII_CHAR_MASK 0x8080808080808080UL
-#elif (SIZEOF_LONG == 4)
-# define ASCII_CHAR_MASK 0x80808080UL
+#if (SIZEOF_SIZE_T == 8)
+# define ASCII_CHAR_MASK 0x8080808080808080ULL
+#elif (SIZEOF_SIZE_T == 4)
+# define ASCII_CHAR_MASK 0x80808080U
 #else
-# error C 'long' size should be either 4 or 8!
+# error C 'size_t' size should be either 4 or 8!
 #endif
 
 /* 10xxxxxx */
@@ -26,7 +26,7 @@
 {
     Py_UCS4 ch;
     const char *s = *inptr;
-    const char *aligned_end = (const char *) _Py_ALIGN_DOWN(end, SIZEOF_LONG);
+    const char *aligned_end = (const char *) _Py_ALIGN_DOWN(end, SIZEOF_SIZE_T);
     STRINGLIB_CHAR *p = dest + *outpos;
 
     while (s < end) {
@@ -36,19 +36,19 @@
             /* Fast path for runs of ASCII characters. Given that common UTF-8
                input will consist of an overwhelming majority of ASCII
                characters, we try to optimize for this case by checking
-               as many characters as a C 'long' can contain.
+               as many characters as a C 'size_t' can contain.
                First, check if we can do an aligned read, as most CPUs have
                a penalty for unaligned reads.
             */
-            if (_Py_IS_ALIGNED(s, SIZEOF_LONG)) {
+            if (_Py_IS_ALIGNED(s, SIZEOF_SIZE_T)) {
                 /* Help register allocation */
                 const char *_s = s;
                 STRINGLIB_CHAR *_p = p;
                 while (_s < aligned_end) {
-                    /* Read a whole long at a time (either 4 or 8 bytes),
+                    /* Read a whole size_t at a time (either 4 or 8 bytes),
                        and do a fast unrolled copy if it only contains ASCII
                        characters. */
-                    unsigned long value = *(const unsigned long *) _s;
+                    size_t value = *(const size_t *) _s;
                     if (value & ASCII_CHAR_MASK)
                         break;
 #if PY_LITTLE_ENDIAN
@@ -56,14 +56,14 @@
                     _p[1] = (STRINGLIB_CHAR)((value >> 8) & 0xFFu);
                     _p[2] = (STRINGLIB_CHAR)((value >> 16) & 0xFFu);
                     _p[3] = (STRINGLIB_CHAR)((value >> 24) & 0xFFu);
-# if SIZEOF_LONG == 8
+# if SIZEOF_SIZE_T == 8
                     _p[4] = (STRINGLIB_CHAR)((value >> 32) & 0xFFu);
                     _p[5] = (STRINGLIB_CHAR)((value >> 40) & 0xFFu);
                     _p[6] = (STRINGLIB_CHAR)((value >> 48) & 0xFFu);
                     _p[7] = (STRINGLIB_CHAR)((value >> 56) & 0xFFu);
 # endif
 #else
-# if SIZEOF_LONG == 8
+# if SIZEOF_SIZE_T == 8
                     _p[0] = (STRINGLIB_CHAR)((value >> 56) & 0xFFu);
                     _p[1] = (STRINGLIB_CHAR)((value >> 48) & 0xFFu);
                     _p[2] = (STRINGLIB_CHAR)((value >> 40) & 0xFFu);
@@ -79,8 +79,8 @@
                     _p[3] = (STRINGLIB_CHAR)(value & 0xFFu);
 # endif
 #endif
-                    _s += SIZEOF_LONG;
-                    _p += SIZEOF_LONG;
+                    _s += SIZEOF_SIZE_T;
+                    _p += SIZEOF_SIZE_T;
                 }
                 s = _s;
                 p = _p;
diff --git a/Objects/stringlib/find_max_char.h b/Objects/stringlib/find_max_char.h
index f4e0a77..3319a46 100644
--- a/Objects/stringlib/find_max_char.h
+++ b/Objects/stringlib/find_max_char.h
@@ -4,14 +4,14 @@
 # error "find_max_char.h is specific to Unicode"
 #endif
 
-/* Mask to quickly check whether a C 'long' contains a
+/* Mask to quickly check whether a C 'size_t' contains a
    non-ASCII, UTF8-encoded char. */
-#if (SIZEOF_LONG == 8)
-# define UCS1_ASCII_CHAR_MASK 0x8080808080808080UL
-#elif (SIZEOF_LONG == 4)
-# define UCS1_ASCII_CHAR_MASK 0x80808080UL
+#if (SIZEOF_SIZE_T == 8)
+# define UCS1_ASCII_CHAR_MASK 0x8080808080808080ULL
+#elif (SIZEOF_SIZE_T == 4)
+# define UCS1_ASCII_CHAR_MASK 0x80808080U
 #else
-# error C 'long' size should be either 4 or 8!
+# error C 'size_t' size should be either 4 or 8!
 #endif
 
 #if STRINGLIB_SIZEOF_CHAR == 1
@@ -21,17 +21,17 @@
 {
     const unsigned char *p = (const unsigned char *) begin;
     const unsigned char *aligned_end =
-            (const unsigned char *) _Py_ALIGN_DOWN(end, SIZEOF_LONG);
+            (const unsigned char *) _Py_ALIGN_DOWN(end, SIZEOF_SIZE_T);
 
     while (p < end) {
-        if (_Py_IS_ALIGNED(p, SIZEOF_LONG)) {
+        if (_Py_IS_ALIGNED(p, SIZEOF_SIZE_T)) {
             /* Help register allocation */
             const unsigned char *_p = p;
             while (_p < aligned_end) {
-                unsigned long value = *(const unsigned long *) _p;
+                size_t value = *(const size_t *) _p;
                 if (value & UCS1_ASCII_CHAR_MASK)
                     return 255;
-                _p += SIZEOF_LONG;
+                _p += SIZEOF_SIZE_T;
             }
             p = _p;
             if (p == end)