Conflicts with XDebug

$ gdb php
(gdb) run -n -d zend_extension=xdebug.so -dextension=modules/couchbase.so --re couchbase
...
Program received signal SIGSEGV, Segmentation fault.
...
(gdb) bt
#0 0x00007fffed533a9e in xdebug_execute_internal (current_execute_data=0x7ffff7f78668, fci=0x0, return_value_used=0)
at /usr/src/debug/php-pecl-xdebug-2.2.5/NTS/xdebug.c:1589
#1 0x000055555582c3c0 in zend_do_fcall_common_helper_SPEC (execute_data=<optimized out>) at /usr/src/debug/php-5.6.1RC1/Zend/zend_vm_execute.h:560
#2 0x00005555557c32d8 in execute_ex (execute_data=0x7ffff7f78668) at /usr/src/debug/php-5.6.1RC1/Zend/zend_vm_execute.h:363
#3 0x0000555555777db9 in dtrace_execute_ex (execute_data=<optimized out>) at /usr/src/debug/php-5.6.1RC1/Zend/zend_dtrace.c:73
#4 0x00007fffed532fcc in xdebug_execute_ex (execute_data=0x7ffff7f78668) at /usr/src/debug/php-pecl-xdebug-2.2.5/NTS/xdebug.c:1437
#5 0x000055555577b61a in zend_eval_stringl (
str=0x7fffed318f10 "/*\n * Various constants used for flags, data-type encoding and decoding, etc...\n * throughout this SDK.\n *\n * @author Brett Lawson <brett19@gmail.com>\n */\n\n/* @internal */ define('COUCHBASE_VAL_MASK"..., str_len=<optimized out>, retval_ptr=retval_ptr@entry=0x0,
string_name=string_name@entry=0x7fffed318e8b "CouchbaseNative") at /usr/src/debug/php-5.6.1RC1/Zend/zend_execute_API.c:1080
#6 0x000055555577b6f6 in zend_eval_string (str=<optimized out>, retval_ptr=retval_ptr@entry=0x0, string_name=string_name@entry=0x7fffed318e8b "CouchbaseNative")
at /usr/src/debug/php-5.6.1RC1/Zend/zend_execute_API.c:1119
#7 0x00007fffed31497c in zm_activate_couchbase (type=<optimized out>, module_number=<optimized out>) at /tmp/couchbase-2.0.0/couchbase.c:63
#8 0x0000555555790060 in zend_activate_modules () at /usr/src/debug/php-5.6.1RC1/Zend/zend_API.c:2414
#9 0x00005555557265da in php_request_startup () at /usr/src/debug/php-5.6.1RC1/main/main.c:1672
#10 0x000055555582da05 in do_cli (argc=7, argv=0x555555b85880) at /usr/src/debug/php-5.6.1RC1/sapi/cli/php_cli.c:965
#11 0x0000555555611550 in main (argc=7, argv=0x555555b85880) at /usr/src/debug/php-5.6.1RC1/sapi/cli/php_cli.c:1378