diff --git a/configure.ac b/configure.ac
index e1b09ef5..d77fd76a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,7 +41,7 @@ AC_CONFIG_MACRO_DIR([m4])
 #------------------------------------------------------------------------------
 
 AC_PROG_CXX
-AM_PROG_AR
+#AM_PROG_AR
 AC_PROG_LIBTOOL
 AM_PROG_CC_C_O
 
diff --git a/include/ecrt.h b/include/ecrt.h
index 0a6e9522..d5de1955 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -55,7 +55,8 @@
  * - Added interface for direct EtherCAT register access: Added data type
  *   ec_reg_request_t and methods ecrt_slave_config_create_reg_request(),
  *   ecrt_reg_request_data(), ecrt_reg_request_state(),
- *   ecrt_reg_request_write() and ecrt_reg_request_read().
+ *   ecrt_reg_request_write(), ecrt_reg_request_read() and the feature flag
+ *   EC_HAVE_REG_ACCESS.
  *
  * Changes in version 1.5:
  *
@@ -154,6 +155,14 @@
  */
 #define EC_HAVE_EMERGENCY
 
+/** Defined, if the register access interface is available.
+ *
+ * I. e. if the methods ecrt_slave_config_create_reg_request(),
+ * ecrt_reg_request_data(), ecrt_reg_request_state(), ecrt_reg_request_write()
+ * and ecrt_reg_request_read() are available.
+ */
+#define EC_HAVE_REG_ACCESS
+
 /*****************************************************************************/
 
 /** End of list marker.