diff --git a/src/if_py_both.h b/src/if_py_both.h
index 6c1aa7f..60375d1 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -12,6 +12,10 @@
  * Common code for if_python.c and if_python3.c.
  */
 
+#if PY_VERSION_HEX < 0x02050000
+typedef int Py_ssize_t;  /* Python 2.4 and earlier don't have this type. */
+#endif
+
 #ifdef FEAT_MBYTE
 # define ENC_OPT p_enc
 #else