diff --git a/lib/libspl/include/sys/feature_tests.h b/lib/libspl/include/sys/feature_tests.h
index a36fd7b8cffb..c9564b2c3269 100644
--- a/lib/libspl/include/sys/feature_tests.h
+++ b/lib/libspl/include/sys/feature_tests.h
@@ -1,41 +1,41 @@
 /*
  * CDDL HEADER START
  *
  * The contents of this file are subject to the terms of the
  * Common Development and Distribution License, Version 1.0 only
  * (the "License").  You may not use this file except in compliance
  * with the License.
  *
  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  * or http://www.opensolaris.org/os/licensing.
  * See the License for the specific language governing permissions
  * and limitations under the License.
  *
  * When distributing Covered Code, include this CDDL HEADER in each
  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  * If applicable, add the following below this CDDL HEADER, with the
  * fields enclosed by brackets "[]" replaced with your own identifying
  * information: Portions Copyright [yyyy] [name of copyright owner]
  *
  * CDDL HEADER END
  */
 /*
  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
 #ifndef _SYS_FEATURE_TESTS_H
 #define	_SYS_FEATURE_TESTS_H
 
 #define	____cacheline_aligned
 #define	__NORETURN		__attribute__((__noreturn__))
 
-#if !defined(fallthrough)
+#if !defined(fallthrough) && !defined(_LIBCPP_VERSION)
 #if defined(HAVE_IMPLICIT_FALLTHROUGH)
 #define	fallthrough		__attribute__((__fallthrough__))
 #else
 #define	fallthrough		((void)0)
 #endif
 #endif
 
 #endif