diff --git a/src/demo/demo.h b/src/demo/demo.h
index ce7f23392a..05cdbe4e94 100644
--- a/src/demo/demo.h
+++ b/src/demo/demo.h
@@ -5,6 +5,7 @@
 #include <assert.h>
 #include <unistd.h>
 #include <limits.h>
+#include <pthread.h>
 #include <stdatomic.h>
 #include <version.h>
 #include <notcurses/notcurses.h>
@@ -146,6 +147,9 @@ int demo_render(struct notcurses* nc);
 
 #define DEMO_RENDER(nc) { int demo_render_err = demo_render(nc); if(demo_render_err){ return demo_render_err; }}
 
+// locked by callers to notcurses_render() and notcurses_refresh(), all internal
+extern pthread_mutex_t demo_render_lock;
+
 // if you won't be doing things, and it's a long sleep, consider using
 // demo_nanosleep(). it updates the HUD, which looks better to the user.
 int demo_nanosleep(struct notcurses* nc, const struct timespec *ts);
diff --git a/src/demo/hud.c b/src/demo/hud.c
index 3f85c29f24..fac4551ab5 100644
--- a/src/demo/hud.c
+++ b/src/demo/hud.c
@@ -5,6 +5,8 @@
 // their mouse. it should always be on the top of the z-stack.
 struct ncplane* hud = NULL;
 
+pthread_mutex_t demo_render_lock = PTHREAD_MUTEX_INITIALIZER;
+
 // while the HUD is grabbed by the mouse, these are set to the position where
 // the grab started. they are reset once the HUD is released.
 static int hud_grab_x = -1;
@@ -438,5 +440,9 @@ int demo_render(struct notcurses* nc){
       return -1;
     }
   }
-  return notcurses_render(nc);
+  // lock against a possible notcurses_refresh() on Ctrl+L
+  pthread_mutex_lock(&demo_render_lock);
+  int ret = notcurses_render(nc);
+  pthread_mutex_unlock(&demo_render_lock);
+  return ret;
 }
diff --git a/src/demo/input.c b/src/demo/input.c
index f934f58af6..3ea5e3620f 100644
--- a/src/demo/input.c
+++ b/src/demo/input.c
@@ -92,16 +92,23 @@ ultramegaok_demo(void* vnc){
       continue;
     }
     if(nckey_mouse_p(ni.id)){
-      handle_mouse(&ni);
-    }else{
-      // if this was about the menu or HUD, pass to them, and continue
-      if(menu_or_hud_key(nc, &ni)){
+      if(handle_mouse(&ni)){
         continue;
       }
-      // go ahead and pass keyboard through to demo, even if it was a 'q'
-      // (this might cause the demo to exit immediately, as is desired)
-      pass_along(&ni);
     }
+    if(id == 'L' && ni.ctrl){
+      pthread_mutex_lock(&demo_render_lock);
+      notcurses_refresh(nc);
+      pthread_mutex_unlock(&demo_render_lock);
+      continue;
+    }
+    // if this was about the menu or HUD, pass to them, and continue
+    if(menu_or_hud_key(nc, &ni)){
+      continue;
+    }
+    // go ahead and pass keyboard through to demo, even if it was a 'q'
+    // (this might cause the demo to exit immediately, as is desired)
+    pass_along(&ni);
   }
   return NULL;
 }
diff --git a/src/lib/internal.h b/src/lib/internal.h
index 05fc859d90..2fb5a8cfc0 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -179,7 +179,7 @@ typedef struct ncselector {
   uint64_t titlechannels;      // title channels
   uint64_t footchannels;       // secondary and footer channels
   uint64_t boxchannels;        // border channels
-  int uarrowy, darrowy, arrowx;// location of scrollarrows, -1 if not present
+  int uarrowy, darrowy, arrowx;// location of scrollarrows, even if not present
 } ncselector;
 
 typedef struct ncdirect {