diff --git a/src/main/resources/assets/computercraft/lua/rom/apis/window.lua b/src/main/resources/assets/computercraft/lua/rom/apis/window.lua
index eaac77eae..4edd393b5 100644
--- a/src/main/resources/assets/computercraft/lua/rom/apis/window.lua
+++ b/src/main/resources/assets/computercraft/lua/rom/apis/window.lua
@@ -413,8 +413,8 @@ function create( parent, nX, nY, nWidth, nHeight, bStartVisible )
     function window.reposition( nNewX, nNewY, nNewWidth, nNewHeight )
         if type( nNewX ) ~= "number" then error( "bad argument #1 (expected number, got " .. type( nNewX ) .. ")", 2 ) end
         if type( nNewY ) ~= "number" then error( "bad argument #2 (expected number, got " .. type( nNewY ) .. ")", 2 ) end
-        if type( nNewWidth ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( nNewWidth ) .. ")", 2 ) end
-        if type( nNewHeight ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( nNewHeight ) .. ")", 2 ) end
+        if nNewWidth ~= nil and type( nNewWidth ) ~= "number" then error( "bad argument #3 (expected number, got " .. type( nNewWidth ) .. ")", 2 ) end
+        if nNewHeight ~= nil and type( nNewHeight ) ~= "number" then error( "bad argument #4 (expected number, got " .. type( nNewHeight ) .. ")", 2 ) end
 
         nX = nNewX
         nY = nNewY