--- ./configure.ac.includedir
+++ ./configure.ac
@@ -1368,7 +1368,7 @@
 EXPANDED_DATADIR=$datadir
 EXPANDED_PHP_CONFIG_FILE_PATH=$(eval echo "$PHP_CONFIG_FILE_PATH")
 EXPANDED_PHP_CONFIG_FILE_SCAN_DIR=$(eval echo "$PHP_CONFIG_FILE_SCAN_DIR")
-INCLUDE_PATH=.:$EXPANDED_PEAR_INSTALLDIR
+INCLUDE_PATH=.:$EXPANDED_PEAR_INSTALLDIR:${EXPANDED_DATADIR}/php:/usr/share/pear:/usr/share/php
 
 exec_prefix=$old_exec_prefix
 libdir=$old_libdir