diff --git a/common/content/buffer.js b/common/content/buffer.js
index 1e6e8d95..00115b22 100644
--- a/common/content/buffer.js
+++ b/common/content/buffer.js
@@ -1303,9 +1303,8 @@ var Buffer = Module("buffer", {
         else
             throw Error();
 
-        let left = "dactylScrollDestX" in elem ? elem.dactylScrollDestX : elem.scrollLeft;
-        if ("dactylScrollDestX" in elem)
-            delete elem.dactylScrollDestX;
+        let left = elem.dactylScrollDestX !== undefined ? elem.dactylScrollDestX : elem.scrollLeft;
+        elem.dactylScrollDestX = undefined;
 
         dactyl.assert(number < 0 ? left > 0 : left < elem.scrollWidth - elem.clientWidth);
         Buffer.scrollTo(elem, left + number * increment, null);
@@ -1332,9 +1331,8 @@ var Buffer = Module("buffer", {
         else
             throw Error();
 
-        let top = "dactylScrollDestY" in elem ? elem.dactylScrollDestY : elem.scrollTop;
-        if ("dactylScrollDestY" in elem)
-            delete elem.dactylScrollDestY;
+        let top = elem.dactylScrollDestY !== undefined ? elem.dactylScrollDestY : elem.scrollTop;
+        elem.dactylScrollDestY = undefined;
 
         dactyl.assert(number < 0 ? top > 0 : top < elem.scrollHeight - elem.clientHeight);
         Buffer.scrollTo(elem, null, top + number * increment);
diff --git a/common/content/events.js b/common/content/events.js
index 89c7ff3a..168e6a59 100644
--- a/common/content/events.js
+++ b/common/content/events.js
@@ -1011,8 +1011,7 @@ var Events = Module("events", {
         */
 
         input: function onInput(event) {
-            if ("dactylKeyPress" in event.originalTarget)
-                delete event.originalTarget.dactylKeyPress;
+            event.originalTarget.dactylKeyPress = undefined;
         },
 
         // this keypress handler gets always called first, even if e.g.
@@ -1027,7 +1026,7 @@ var Events = Module("events", {
                 let elem = event.originalTarget;
                 elem.dactylKeyPress = elem.value;
                 util.timeout(function () {
-                    if ("dactylKeyPress" in elem && elem.value !== elem.dactylKeyPress)
+                    if (elem.value !== elem.dactylKeyPress)
                         events.dispatch(elem, events.create(elem.ownerDocument, "input"));
                     delete events.dactylKeyPress;
                 });