diff --git a/net.c b/net.c
index 5308031..d8caa01 100644
--- a/net.c
+++ b/net.c
@@ -606,6 +606,7 @@ static char *new_game_desc(game_params *params, random_state *rs,
         }
     }
     assert(p - desc <= w*h*3);
+    *p = '\0';
 
     sfree(tiles);
     sfree(barriers);
diff --git a/netslide.c b/netslide.c
index 6ae9569..b72706a 100644
--- a/netslide.c
+++ b/netslide.c
@@ -645,6 +645,7 @@ static char *new_game_desc(game_params *params, random_state *rs,
         }
     }
     assert(p - desc <= w*h*3);
+    *p = '\0';
 
     sfree(tiles);
     sfree(barriers);