diff --git a/src/diff/cell.ts b/src/diff/cell.ts
index fdbf1eb..a3e2b07 100644
--- a/src/diff/cell.ts
+++ b/src/diff/cell.ts
@@ -60,8 +60,16 @@ class CodeMirrorSplitDiffWidget extends BaseDiffWidget {
         extensions: [
           basicSetup,
           python(),
-          EditorView.editable.of(false),
-          jupyterTheme
+          EditorView.editable.of(true),
+          jupyterTheme,
+          EditorView.updateListener.of(update => {
+            if (update.docChanged) {
+              const newText = update.state.doc.toString();
+
+              this._modifiedCode = newText;
+              this._newSource = newText;
+            }
+          })
         ]
       },
       parent: this.node
diff --git a/src/widget.ts b/src/widget.ts
index e37ef67..a744f16 100644
--- a/src/widget.ts
+++ b/src/widget.ts
@@ -100,7 +100,7 @@ export abstract class BaseDiffWidget extends Widget {
    */
   public onAcceptClick(): void {
     if (this._cell) {
-      this._cell.sharedModel.setSource(this._newSource);
+      this._cell.sharedModel.setSource(this._newSource || this._originalSource);
       this._closeDiffView();
     }
   }
@@ -191,9 +191,9 @@ export abstract class BaseDiffWidget extends Widget {
   private _cell: ICellModel;
   private _cellFooterTracker: ICellFooterTracker;
   private _originalSource: string;
-  private _newSource: string;
   private _showActionButtons: boolean;
   private _openDiff: boolean;
   private _toggleButton: ToolbarButton | null = null;
   private _trans: TranslationBundle;
+  public _newSource: string;
 }