diff --git a/browser/devtools/styleinspector/test/browser_ruleview_livepreview.js b/browser/devtools/styleinspector/test/browser_ruleview_livepreview.js
index 622bfc8b18fa..c51e70e6fd62 100644
--- a/browser/devtools/styleinspector/test/browser_ruleview_livepreview.js
+++ b/browser/devtools/styleinspector/test/browser_ruleview_livepreview.js
@@ -37,7 +37,6 @@ add_task(function*() {
   }
 });
 
-
 function* testLivePreviewData(data, ruleView, selector) {
   let testElement = getNode(selector);
   let idRuleEditor = getRuleViewRuleEditor(ruleView, 1);
@@ -57,10 +56,13 @@ function* testLivePreviewData(data, ruleView, selector) {
     EventUtils.synthesizeKey("VK_RETURN", {});
   }
 
-  // This wait is an orange waiting to happen, but it might take a few event
-  // loop spins in either the client or parent process before we see the
-  // updated value.
-  yield wait(1);
+  // Wait for the modifyproperties request to complete before
+  // checking the computed style.
+  for (let rule of ruleView._elementStyle.rules) {
+    if (rule._applyingModifications) {
+      yield rule._applyingModifications;
+    }
+  }
 
   // While the editor is still focused in, the display should have changed already
   is((yield getComputedStyleProperty(selector, null, "display")),