diff --git a/src/unixcomm.c b/src/unixcomm.c
index 4edcbee..4a8effd 100644
--- a/src/unixcomm.c
+++ b/src/unixcomm.c
@@ -7,7 +7,7 @@ Unix Interface Communications
 
 */
 
-// Don't compile this at all under DOS.
+/* Don't compile this at all under DOS. */
 #ifndef DOS
 
 /************************************************************************/