diff --git a/ChangeLog b/ChangeLog
index b739fedf..e9778ac4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,8 @@
 
 	* configure.ac: Fix typo when substituting value for unsigned 8 bit type.
 	Added support for a TIFF_PTRDIFF_T type to use when doing pointer arithmetic.
+	Added support for a TIFF_SSIZE_T in order to return memory sizes but still
+	allow returning -1 for errors.
 	* libtiff/tiffconf.vc.h: Add porting type defintions for WIN32.
 
 2007-06-25  Bob Friesenhahn  <bfriesen@simple.dallas.tx.us>
diff --git a/build/Makefile.in b/build/Makefile.in
index 49edf393..81935835 100644
--- a/build/Makefile.in
+++ b/build/Makefile.in
@@ -14,7 +14,7 @@
 
 @SET_MAKE@
 
-# $Id: Makefile.in,v 1.5 2007-06-26 20:05:38 bfriesen Exp $
+# $Id: Makefile.in,v 1.6 2007-06-26 22:52:12 bfriesen Exp $
 #
 # Tag Image File Format (TIFF) Software
 #
diff --git a/configure b/configure
index 1b342686..9f2b79a0 100755
--- a/configure
+++ b/configure
@@ -24877,6 +24877,25 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+# Determine TIFF equivalent of ssize_t
+{ echo "$as_me:$LINENO: checking for signed size type" >&5
+echo $ECHO_N "checking for signed size type... $ECHO_C" >&6; }
+SSIZE_T='unknown'
+if test $ac_cv_sizeof_signed_long -eq $ac_cv_sizeof_unsigned_char_p
+then
+  SSIZE_T='signed long'
+elif test $ac_cv_sizeof_signed_long_long -eq $ac_cv_sizeof_unsigned_char_p
+then
+  SSIZE_T='signed long long'
+fi
+{ echo "$as_me:$LINENO: result: $SSIZE_T" >&5
+echo "${ECHO_T}$SSIZE_T" >&6; }
+
+cat >>confdefs.h <<_ACEOF
+#define TIFF_SSIZE_T $SSIZE_T
+_ACEOF
+
+
 # Determine the type to use for the difference between two pointers.
 # We will default to the POSIX ptrdiff_t if it is available, but will
 # be prepared for the case when it is not.
@@ -24940,13 +24959,7 @@ fi
 
 if test $PTRDIFF_T = unknown
 then
-  if test $ac_cv_sizeof_signed_long -eq $ac_cv_sizeof_unsigned_char_p
-  then
-    PTRDIFF_T='signed long'
-  elif test $ac_cv_sizeof_signed_long_long -eq $ac_cv_sizeof_unsigned_char_p
-  then
-    PTRDIFF_T='signed long long'
-  fi
+  PTRDIFF_T=$SSIZE_T
 fi
 { echo "$as_me:$LINENO: checking for pointer difference type" >&5
 echo $ECHO_N "checking for pointer difference type... $ECHO_C" >&6; }
diff --git a/configure.ac b/configure.ac
index 57a9e47c..c6a94e79 100644
--- a/configure.ac
+++ b/configure.ac
@@ -208,6 +208,19 @@ fi
 AC_MSG_RESULT($UINT64_T)
 AC_DEFINE_UNQUOTED(TIFF_UINT64_T,$UINT64_T,[Unsigned 64-bit type])
 
+# Determine TIFF equivalent of ssize_t
+AC_MSG_CHECKING(for signed size type)
+SSIZE_T='unknown'
+if test $ac_cv_sizeof_signed_long -eq $ac_cv_sizeof_unsigned_char_p
+then
+  SSIZE_T='signed long'
+elif test $ac_cv_sizeof_signed_long_long -eq $ac_cv_sizeof_unsigned_char_p
+then
+  SSIZE_T='signed long long'
+fi
+AC_MSG_RESULT($SSIZE_T)
+AC_DEFINE_UNQUOTED(TIFF_SSIZE_T,$SSIZE_T,[Signed size type])
+
 # Determine the type to use for the difference between two pointers.
 # We will default to the POSIX ptrdiff_t if it is available, but will
 # be prepared for the case when it is not.
@@ -215,13 +228,7 @@ PTRDIFF_T='unknown'
 AC_CHECK_TYPE(ptrdiff_t,[PTRDIFF_T=ptrdiff_t])
 if test $PTRDIFF_T = unknown
 then
-  if test $ac_cv_sizeof_signed_long -eq $ac_cv_sizeof_unsigned_char_p
-  then
-    PTRDIFF_T='signed long'
-  elif test $ac_cv_sizeof_signed_long_long -eq $ac_cv_sizeof_unsigned_char_p
-  then
-    PTRDIFF_T='signed long long'
-  fi
+  PTRDIFF_T=$SSIZE_T
 fi
 AC_MSG_CHECKING(for pointer difference type)
 AC_MSG_RESULT($PTRDIFF_T)
diff --git a/contrib/dbs/xtiff/Makefile.in b/contrib/dbs/xtiff/Makefile.in
index 8bb175a6..ccb0bbc4 100644
--- a/contrib/dbs/xtiff/Makefile.in
+++ b/contrib/dbs/xtiff/Makefile.in
@@ -14,7 +14,7 @@
 
 @SET_MAKE@
 
-# $Id: Makefile.in,v 1.40 2007-06-26 20:05:39 bfriesen Exp $
+# $Id: Makefile.in,v 1.41 2007-06-26 22:52:13 bfriesen Exp $
 #
 # Tag Image File Format (TIFF) Software
 #
diff --git a/html/Makefile.in b/html/Makefile.in
index 3c06b4b8..2abd2c53 100644
--- a/html/Makefile.in
+++ b/html/Makefile.in
@@ -14,7 +14,7 @@
 
 @SET_MAKE@
 
-# $Id: Makefile.in,v 1.53 2007-06-26 20:05:40 bfriesen Exp $
+# $Id: Makefile.in,v 1.54 2007-06-26 22:52:13 bfriesen Exp $
 #
 # Tag Image File Format (TIFF) Software
 #
diff --git a/libtiff/tif_config.h.in b/libtiff/tif_config.h.in
index e9ce813b..4c0fcdcf 100644
--- a/libtiff/tif_config.h.in
+++ b/libtiff/tif_config.h.in
@@ -265,6 +265,9 @@
 /* Pointer difference type */
 #undef TIFF_PTRDIFF_T
 
+/* Signed size type */
+#undef TIFF_SSIZE_T
+
 /* Unsigned 16-bit type */
 #undef TIFF_UINT16_T
 
diff --git a/libtiff/tiffconf.h.in b/libtiff/tiffconf.h.in
index 0d573d7e..6da9c5a6 100644
--- a/libtiff/tiffconf.h.in
+++ b/libtiff/tiffconf.h.in
@@ -31,6 +31,9 @@
 /* Unsigned 8-bit type */
 #undef TIFF_UINT8_T
 
+/* Signed size type */
+#undef TIFF_SSIZE_T
+
 /* Pointer difference type */
 #undef TIFF_PTRDIFF_T
 
diff --git a/libtiff/tiffconf.vc.h b/libtiff/tiffconf.vc.h
index 8680b56d..efec8188 100644
--- a/libtiff/tiffconf.vc.h
+++ b/libtiff/tiffconf.vc.h
@@ -46,6 +46,9 @@
 /* Unsigned 64-bit type */
 #define TIFF_UINT64_T unsigned __int64
 
+/* Signed size type */
+#define TIFF_SSIZE_T signed long
+
 /* Pointer difference type */
 #define TIFF_PTRDIFF_T long
 
diff --git a/libtiff/tiffio.h b/libtiff/tiffio.h
index e7a6e3de..bbcdb698 100644
--- a/libtiff/tiffio.h
+++ b/libtiff/tiffio.h
@@ -1,4 +1,4 @@
-/* $Id: tiffio.h,v 1.69 2007-06-26 20:05:40 bfriesen Exp $ */
+/* $Id: tiffio.h,v 1.70 2007-06-26 22:52:13 bfriesen Exp $ */
 
 /*
  * Copyright (c) 1988-1997 Sam Leffler
@@ -60,7 +60,7 @@ typedef struct tiff TIFF;
  */
 /* this is the machine addressing size type, only it's signed, so make it int32
    on 32bit machines, int64 on 64bit machines */
-typedef TIFF_PTRDIFF_T tmsize_t;
+typedef TIFF_SSIZE_T tmsize_t;
 /* the following are depriciated and should be replaced by their defining
    counterparts */
 typedef uint32 ttag_t;          /* directory tag */