diff --git a/ChangeLog.txt b/ChangeLog.txt
index 309b5e21..1619a46b 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -32,10 +32,11 @@ SIMD-enabled libjpeg-turbo MIPS build was executed with the -nosmooth option on
 a MIPS machine that lacked DSPr2 support.  The MIPS SIMD routines for h2v1 and
 h2v2 merged upsampling were not properly checking for the existence of DSPr2.
 
-[6] Performance has been improved significantly on 64-bit Mac platforms
-(particularly compression performance.)  Due to an oversight, the 64-bit
-version of the accelerated Huffman codec was not being compiled in when
-libjpeg-turbo was built on OS X.  Oops.
+[6] Performance has been improved significantly on 64-bit non-Linux and
+non-Windows platforms (generally 10-20% faster compression and 5-10% faster
+decompression.)  Due to an oversight, the 64-bit version of the accelerated
+Huffman codec was not being compiled in when libjpeg-turbo was built on
+platforms other than Windows or Linux.  Oops.
 
 [7] Fixed an extremely rare bug in the Huffman encoder that caused 64-bit
 builds of libjpeg-turbo to incorrectly encode a few specific test images when
diff --git a/configure.ac b/configure.ac
index f2b8cf2e..6ef4b5c6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -50,6 +50,8 @@ if test "x$exec_prefix" = "xNONE"; then
   exec_prefix=${prefix}
 fi
 
+AC_CHECK_SIZEOF(size_t)
+
 if test "x${libdir}" = 'x${exec_prefix}/lib' -o "x${libdir}" = 'x${prefix}/lib'; then
   LIBDIR=`eval echo ${libdir}`
   LIBDIR=`eval echo $LIBDIR`
@@ -58,10 +60,9 @@ if test "x${libdir}" = 'x${exec_prefix}/lib' -o "x${libdir}" = 'x${prefix}/lib';
       darwin*)
         ;;
       *)
-        AC_CHECK_SIZEOF(long)
-        if test "${ac_cv_sizeof_long}" = "8"; then
+        if test "${ac_cv_sizeof_size_t}" = "8"; then
           libdir='${exec_prefix}/lib64'
-        elif test "${ac_cv_sizeof_long}" = "4"; then
+        elif test "${ac_cv_sizeof_size_t}" = "4"; then
           libdir='${exec_prefix}/lib32'
         fi
         ;;
diff --git a/jchuff.c b/jchuff.c
index 23c66591..4ecc18d6 100644
--- a/jchuff.c
+++ b/jchuff.c
@@ -21,9 +21,6 @@
 #include "jpeglib.h"
 #include "jchuff.h"             /* Declarations shared with jcphuff.c */
 #include <limits.h>
-#ifdef HAVE_STDINT_H
-#include <stdint.h>
-#endif
 
 /*
  * NOTE: If USE_CLZ_INTRINSIC is defined, then clz/bsr instructions will be
@@ -379,11 +376,11 @@ dump_buffer (working_state * state)
   } \
 }
 
-#if !defined(_WIN32) && !defined(__WORDSIZE)
-#error __WORDSIZE is not defined
+#if !defined(_WIN32) && !defined(SIZEOF_SIZE_T)
+#error Cannot determine word size
 #endif
 
-#if __WORDSIZE==64 || defined(_WIN64)
+#if SIZEOF_SIZE_T==8 || defined(_WIN64)
 
 #define EMIT_BITS(code, size) { \
   CHECKBUF47() \
diff --git a/jconfig.h.in b/jconfig.h.in
index fbf64a58..b99a87e1 100644
--- a/jconfig.h.in
+++ b/jconfig.h.in
@@ -32,9 +32,6 @@
 /* Define to 1 if you have the <stdlib.h> header file. */
 #undef HAVE_STDLIB_H
 
-/* Define to 1 if you have the <stdint.h> header file. */
-#undef HAVE_STDINT_H
-
 /* Define to 1 if the system has the type `unsigned char'. */
 #undef HAVE_UNSIGNED_CHAR
 
@@ -71,3 +68,6 @@
 
 /* Define to `unsigned int' if <sys/types.h> does not define. */
 #undef size_t
+
+/* The size of `size_t', as computed by sizeof. */
+#undef SIZEOF_SIZE_T
diff --git a/jdhuff.c b/jdhuff.c
index 03e39492..cbdce7d4 100644
--- a/jdhuff.c
+++ b/jdhuff.c
@@ -22,9 +22,6 @@
 #include "jdhuff.h"             /* Declarations shared with jdphuff.c */
 #include "jpegcomp.h"
 #include "jstdhuff.c"
-#ifdef HAVE_STDINT_H
-#include <stdint.h>
-#endif
 
 
 /*
@@ -422,11 +419,7 @@ jpeg_fill_bit_buffer (bitread_working_state * state,
   } \
 }
 
-#if !defined(_WIN32) && !defined(__WORDSIZE)
-#error __WORDSIZE is not defined
-#endif
-
-#if __WORDSIZE == 64 || defined(_WIN64)
+#if SIZEOF_SIZE_T==8 || defined(_WIN64)
 
 /* Pre-fetch 48 bytes, because the holding register is 64-bit */
 #define FILL_BIT_BUFFER_FAST \
diff --git a/jdhuff.h b/jdhuff.h
index f2805e46..c7f3d500 100644
--- a/jdhuff.h
+++ b/jdhuff.h
@@ -67,7 +67,11 @@ EXTERN(void) jpeg_make_d_derived_tbl
  * necessary.
  */
 
-#if __WORDSIZE == 64 || defined(_WIN64)
+#if !defined(_WIN32) && !defined(SIZEOF_SIZE_T)
+#error Cannot determine word size
+#endif
+
+#if SIZEOF_SIZE_T==8 || defined(_WIN64)
 
 typedef size_t bit_buf_type;    /* type of bit-extraction buffer */
 #define BIT_BUF_SIZE  64                /* size of buffer in bits */