diff --git a/lib/codemirror.js b/lib/codemirror.js
index de21497c2c4a6e82ca31305a8c7c85781a284bb2..b464356b3eb048425e57d8a9fc4d7a600a97f0bd 100644
--- a/lib/codemirror.js
+++ b/lib/codemirror.js
@@ -3770,7 +3770,7 @@
     var screenleft = cm.curOp && cm.curOp.scrollLeft != null ? cm.curOp.scrollLeft : display.scroller.scrollLeft;
     var screenw = display.scroller.clientWidth - scrollerCutOff - display.gutters.offsetWidth;
     var tooWide = x2 - x1 > screenw;
-    if (tooWide) x2 = x1 + screen;
+    if (tooWide) x2 = x1 + screenw;
     if (x1 < 10)
       result.scrollLeft = 0;
     else if (x1 < screenleft)