diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index 8b57a59ee39..8b593f1f451 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -1277,7 +1277,7 @@ static PHP_INI_MH(OnUpdate_zlib_output_compression)
 	} else {
 		int_value = (int) zend_ini_parse_quantity_warn(new_value, entry->name);
 	}
-	ini_value = zend_ini_string("output_handler", sizeof("output_handler"), 0);
+	ini_value = zend_ini_string("output_handler", sizeof("output_handler") - 1, 0);
 
 	if (ini_value && *ini_value && int_value) {
 		php_error_docref("ref.outcontrol", E_CORE_ERROR, "Cannot use both zlib.output_compression and output_handler together!!");