diff --git a/Include/pyport.h b/Include/pyport.h
index be6c51f..8f8e514 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -126,7 +126,7 @@
  * Py_ssize_t on the platform.
  */
 #ifndef PY_FORMAT_SIZE_T
-#   if SIZEOF_SIZE_T == SIZEOF_INT
+#   if SIZEOF_SIZE_T == SIZEOF_INT && !defined(__APPLE__)
 #       define PY_FORMAT_SIZE_T ""
 #   elif SIZEOF_SIZE_T == SIZEOF_LONG
 #       define PY_FORMAT_SIZE_T "l"
diff --git a/Misc/NEWS b/Misc/NEWS
index 685daf6..42b366d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -16,6 +16,8 @@
   not being recognized as a keyword after, e.g., this statement:
   from __future__ import division, with_statement
 
+- Fix %zd string formatting on Mac OS X so it prints negative numbers.
+
 - Allow exception instances to be directly sliced again.
 
 
diff --git a/configure b/configure
index 794a0be..6b96c77 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 51173 .
+# From configure.in Revision: 51727 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.59 for python 2.5.
 #
@@ -22110,12 +22110,26 @@
 
 int main()
 {
-    char buffer[4];
+    char buffer[256];
+
+#ifdef HAVE_SSIZE_T
+typedef ssize_t Py_ssize_t;
+#elif SIZEOF_VOID_P == SIZEOF_LONG
+typedef long Py_ssize_t;
+#else
+typedef int Py_ssize_t;
+#endif
 
     if(sprintf(buffer, "%zd", (size_t)123) < 0)
        	return 1;
 
-    if (strncmp(buffer, "123", 3))
+    if (strcmp(buffer, "123"))
+	return 1;
+
+    if (sprintf(buffer, "%zd", (Py_ssize_t)-123) < 0)
+       	return 1;
+
+    if (strcmp(buffer, "-123"))
 	return 1;
 
     return 0;
diff --git a/configure.in b/configure.in
index 410f1af..711e19e 100644
--- a/configure.in
+++ b/configure.in
@@ -3352,14 +3352,28 @@
 
 int main()
 {
-    char buffer[4];
+    char buffer[256];
+
+#ifdef HAVE_SSIZE_T
+typedef ssize_t Py_ssize_t;
+#elif SIZEOF_VOID_P == SIZEOF_LONG
+typedef long Py_ssize_t;
+#else
+typedef int Py_ssize_t;
+#endif
 
     if(sprintf(buffer, "%zd", (size_t)123) < 0)
        	return 1;
 
-    if (strncmp(buffer, "123", 3))
+    if (strcmp(buffer, "123"))
 	return 1;
-    
+
+    if (sprintf(buffer, "%zd", (Py_ssize_t)-123) < 0)
+       	return 1;
+
+    if (strcmp(buffer, "-123"))
+	return 1;
+
     return 0;
 }],
 [AC_MSG_RESULT(yes)