diff --git a/target/m68k/m68k-semi.c b/target/m68k/m68k-semi.c
index 239f6e44e9..80cd8d70db 100644
--- a/target/m68k/m68k-semi.c
+++ b/target/m68k/m68k-semi.c
@@ -15,6 +15,10 @@
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ *  The semihosting protocol implemented here is described in the
+ *  libgloss sources:
+ *  https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=libgloss/m68k/m68k-semi.txt;hb=HEAD
  */
 
 #include "qemu/osdep.h"