--- a/devtools/client/shared/components/splitter/Draggable.js
+++ b/devtools/client/shared/components/splitter/Draggable.js
@@ -23,31 +23,45 @@ class Draggable extends Component {
   constructor(props) {
     super(props);
     this.startDragging = this.startDragging.bind(this);
     this.onMove = this.onMove.bind(this);
     this.onUp = this.onUp.bind(this);
   }
 
   startDragging(ev) {
+    if (this.isDragging) {
+      return;
+    }
+    this.isDragging = true;
+
     ev.preventDefault();
     const doc = ReactDOM.findDOMNode(this).ownerDocument;
     doc.addEventListener("mousemove", this.onMove);
     doc.addEventListener("mouseup", this.onUp);
     this.props.onStart && this.props.onStart();
   }
 
   onMove(ev) {
+    if (!this.isDragging) {
+      return;
+    }
+
     ev.preventDefault();
     // Use viewport coordinates so, moving mouse over iframes
     // doesn't mangle (relative) coordinates.
     this.props.onMove(ev.clientX, ev.clientY);
   }
 
   onUp(ev) {
+    if (!this.isDragging) {
+      return;
+    }
+    this.isDragging = false;
+
     ev.preventDefault();
     const doc = ReactDOM.findDOMNode(this).ownerDocument;
     doc.removeEventListener("mousemove", this.onMove);
     doc.removeEventListener("mouseup", this.onUp);
     this.props.onStop && this.props.onStop();
   }
 
   render() {