diff --git a/src/rx/rx_atomic.h b/src/rx/rx_atomic.h
index e59aad632b..0b2d6af8c6 100644
--- a/src/rx/rx_atomic.h
+++ b/src/rx/rx_atomic.h
@@ -22,6 +22,9 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#ifndef OPENAFS_RX_ATOMIC_H
+#define OPENAFS_RX_ATOMIC_H 1
+
 #define RX_ATOMIC_INIT(i) { (i) }
 
 #ifdef AFS_NT40_ENV
@@ -280,3 +283,5 @@ rx_atomic_sub(rx_atomic_t *atomic, int change) {
 }
 
 #endif
+
+#endif