diff --git a/src/lua/core/computer.lua b/src/lua/core/computer.lua
index 2697daf..b11172a 100644
--- a/src/lua/core/computer.lua
+++ b/src/lua/core/computer.lua
@@ -111,11 +111,14 @@ function computer.signalTransformers.key_down(s, a, ascii, key, user)
   end
   if ascii == 27 then
     inesc = true
+    return nil
   elseif inesc then
     if ascii < 48 and ascii > 57 and ascii ~= 59 then
       inesc = false
       key = escmap[ascii] or 0
       ascii = 0
+    else
+      return nil
     end
   end
   return s, a, math.floor(asciitr[ascii] or ascii), keymap[ascii] or key, user
@@ -125,13 +128,28 @@ function computer.signalTransformers.key_up(s, a, ascii, key, user)
   if key ~= -1 then
     return s, a, ascii, key, user
   end
+  if ascii == 27 then
+    inesc = true
+    return nil
+  elseif inesc then
+    if ascii < 48 and ascii > 57 and ascii ~= 59 then
+      inesc = false
+      key = escmap[ascii] or 0
+      ascii = 0
+    else
+      return nil
+    end
+  end
   return s, a, math.floor(asciitr[ascii] or ascii), keymap[ascii] or key, user
 end
 
 -----
 
 function api.pushSignal(s, ...)
-  signalQueue[#signalQueue + 1] = {computer.signalTransformers[s](s, ...)}
+  local result = table.pack(computer.signalTransformers[s](s, ...))
+  if result.n == 0 then return end
+  result.n = nil
+  signalQueue[#signalQueue + 1] = result
 end
 
 function api.pullSignal(timeout)