diff --git a/m-snapshot.h b/m-snapshot.h
index 726e524a..88958cd5 100644
--- a/m-snapshot.h
+++ b/m-snapshot.h
@@ -22,8 +22,8 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
-#ifndef MSTARLIB_SNAPSHOT
-#define MSTARLIB_SNAPSHOT
+#ifndef MSTARLIB_SNAPSHOT_H
+#define MSTARLIB_SNAPSHOT_H
 
 #include "m-atomic.h"
 #include "m-core.h"