diff --git a/browser/devtools/styleinspector/rule-view.js b/browser/devtools/styleinspector/rule-view.js
index 3bf2e4fdabc..d6d903a47b3 100644
--- a/browser/devtools/styleinspector/rule-view.js
+++ b/browser/devtools/styleinspector/rule-view.js
@@ -2370,7 +2370,11 @@ UserProperties.prototype = {
 
     if (entry && aName in entry) {
       let item = entry[aName];
-      return item || aDefault;
+      if (item != aDefault) {
+        delete entry[aName];
+        return aDefault;
+      }
+      return item;
     }
     return aDefault;
   },
diff --git a/browser/devtools/styleinspector/test/browser.ini b/browser/devtools/styleinspector/test/browser.ini
index 0c6961d1012..5c2940d797c 100644
--- a/browser/devtools/styleinspector/test/browser.ini
+++ b/browser/devtools/styleinspector/test/browser.ini
@@ -64,3 +64,4 @@ support-files =
   sourcemaps.scss
 [browser_computedview_original_source_link.js]
 [browser_bug946331_close_tooltip_on_new_selection.js]
+[browser_bug942297_user_property_reset.js]
diff --git a/browser/devtools/styleinspector/test/browser_bug942297_user_property_reset.js b/browser/devtools/styleinspector/test/browser_bug942297_user_property_reset.js
new file mode 100644
index 00000000000..16dc7663e21
--- /dev/null
+++ b/browser/devtools/styleinspector/test/browser_bug942297_user_property_reset.js
@@ -0,0 +1,128 @@
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+ http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that user set style properties can be changed from the markup-view and
+// don't survive page reload
+
+let {devtools} = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});
+let promise = devtools.require("sdk/core/promise");
+let {Task} = Cu.import("resource://gre/modules/Task.jsm", {});
+
+let TEST_PAGE = [
+  "data:text/html,",
+  "<p id='id1' style='width:200px;'>element 1</p>",
+  "<p id='id2' style='width:100px;'>element 2</p>"
+].join("");
+
+let doc;
+let inspector;
+let ruleView;
+let markupView;
+
+function test() {
+  waitForExplicitFinish();
+
+  gBrowser.selectedTab = gBrowser.addTab();
+  gBrowser.selectedBrowser.addEventListener("load", function onload(evt) {
+    gBrowser.selectedBrowser.removeEventListener("load", onload, true);
+    doc = content.document;
+    waitForFocus(() => {
+      openRuleView((aInspector, aView) => {
+        inspector = aInspector;
+        ruleView = aView;
+        markupView = inspector.markup;
+
+        Task.spawn(function() {
+          yield selectElement("id1");
+          yield modifyRuleViewWidth("300px");
+          assertRuleAndMarkupViewWidth("id1", "300px");
+          yield selectElement("id2");
+          assertRuleAndMarkupViewWidth("id2", "100px");
+          yield modifyRuleViewWidth("50px");
+          assertRuleAndMarkupViewWidth("id2", "50px");
+
+          yield reloadPage();
+          yield selectElement("id1");
+          assertRuleAndMarkupViewWidth("id1", "200px");
+          yield selectElement("id2");
+          assertRuleAndMarkupViewWidth("id2", "100px");
+
+          finishTest();
+        }).then(null, Cu.reportError);
+      });
+    }, content);
+  }, true);
+
+  content.location = TEST_PAGE;
+}
+
+function finishTest() {
+  doc = inspector = ruleView = markupView = null;
+  gBrowser.removeCurrentTab();
+  finish();
+}
+
+function selectElement(id) {
+  let deferred = promise.defer();
+  inspector.selection.setNode(doc.getElementById(id));
+  inspector.once("inspector-updated", deferred.resolve);
+  return deferred.promise;
+}
+
+function getStyleRule() {
+  return ruleView.doc.querySelector(".ruleview-rule");
+}
+
+function modifyRuleViewWidth(value) {
+  let deferred = promise.defer();
+
+  let valueSpan = getStyleRule().querySelector(".ruleview-propertyvalue");
+  waitForEditorFocus(valueSpan.parentNode, () => {
+    let editor = inplaceEditor(valueSpan);
+    editor.input.value = value;
+    waitForEditorBlur(editor, () => {
+      // Changing the style will refresh the markup view, let's wait for that
+      inspector.once("markupmutation", () => {
+        waitForEditorBlur({input: ruleView.doc.activeElement}, deferred.resolve);
+        EventUtils.sendKey("escape");
+      });
+    });
+    EventUtils.sendKey("return");
+  });
+  valueSpan.click();
+
+  return deferred.promise;
+}
+
+function getContainerStyleAttrValue(id) {
+  let front = markupView.walker.frontForRawNode(doc.getElementById(id));
+  let container = markupView.getContainer(front);
+
+  let attrIndex = 0;
+  for (let attrName of container.elt.querySelectorAll(".attr-name")) {
+    if (attrName.textContent === "style") {
+      return container.elt.querySelectorAll(".attr-value")[attrIndex];
+    }
+    attrIndex ++;
+  }
+}
+
+function assertRuleAndMarkupViewWidth(id, value) {
+  let valueSpan = getStyleRule().querySelector(".ruleview-propertyvalue");
+  is(valueSpan.textContent, value, "Rule-view style width is " + value + " as expected");
+
+  let attr = getContainerStyleAttrValue(id);
+  is(attr.textContent.replace(/\s/g, ""), "width:" + value + ";", "Markup-view style attribute width is " + value);
+}
+
+function reloadPage() {
+  let deferred = promise.defer();
+  inspector.once("new-root", () => {
+    doc = content.document;
+    markupView = inspector.markup;
+    markupView._waitForChildren().then(deferred.resolve);
+  });
+  content.location.reload();
+  return deferred.promise;
+}