diff --git a/src/static/js/Changeset.js b/src/static/js/Changeset.js
index 366ad15f9..4d5487f82 100644
--- a/src/static/js/Changeset.js
+++ b/src/static/js/Changeset.js
@@ -255,20 +255,20 @@ exports.checkRep = function (cs) {
     var o = iter.next();
     switch (o.opcode) {
     case '=':
+      exports.assert(o.chars >= o.lines, o.chars, " chars and ", o.lines, " lines in op ",cs);
       oldPos += o.chars;
       calcNewLen += o.chars;
       break;
     case '-':
+      exports.assert(o.chars >= o.lines, o.chars, " chars and ", o.lines, " lines in op ",cs);
       oldPos += o.chars;
       exports.assert(oldPos < oldLen, oldPos, " >= ", oldLen, " in ", cs);
       break;
     case '+':
-      {
-        calcNewLen += o.chars;
-        numInserted += o.chars;
-        exports.assert(calcNewLen < newLen, calcNewLen, " >= ", newLen, " in ", cs);
-        break;
-      }
+      exports.assert(o.chars >= o.lines, o.chars, " chars and ", o.lines, " lines in op ",cs);
+      calcNewLen += o.chars;
+      exports.assert(calcNewLen < newLen, calcNewLen, " >= ", newLen, " in ", cs);
+      break;
     }
     assem.append(o);
   }