diff --git a/src/SelectionManager.test.ts b/src/SelectionManager.test.ts
index c42735d5..8735e894 100644
--- a/src/SelectionManager.test.ts
+++ b/src/SelectionManager.test.ts
@@ -30,6 +30,7 @@ class TestSelectionManager extends SelectionManager {
 
   public selectLineAt(line: number): void { this._selectLineAt(line); }
   public selectWordAt(coords: [number, number]): void { this._selectWordAt(coords, true); }
+  public areCoordsInSelection(coords: [number, number], start: [number, number], end: [number, number]): boolean { return this._areCoordsInSelection(coords, start, end); }
 
   // Disable DOM interaction
   public enable(): void {}
@@ -478,5 +479,17 @@ describe('SelectionManager', () => {
       assert.equal(selectionManager.selectionText, 'a\n😁\nc');
     });
   });
+
+  describe('_areCoordsInSelection', () => {
+    it('should return whether coords are in the selection', () => {
+      assert.isFalse(selectionManager.areCoordsInSelection([0, 0], [2, 0], [2, 1]));
+      assert.isFalse(selectionManager.areCoordsInSelection([1, 0], [2, 0], [2, 1]));
+      assert.isTrue(selectionManager.areCoordsInSelection([2, 0], [2, 0], [2, 1]));
+      assert.isTrue(selectionManager.areCoordsInSelection([10, 0], [2, 0], [2, 1]));
+      assert.isTrue(selectionManager.areCoordsInSelection([0, 1], [2, 0], [2, 1]));
+      assert.isTrue(selectionManager.areCoordsInSelection([1, 1], [2, 0], [2, 1]));
+      assert.isFalse(selectionManager.areCoordsInSelection([2, 1], [2, 0], [2, 1]));
+    });
+  });
 });
 
diff --git a/src/SelectionManager.ts b/src/SelectionManager.ts
index bfb57177..86be0c48 100644
--- a/src/SelectionManager.ts
+++ b/src/SelectionManager.ts
@@ -289,9 +289,14 @@ export class SelectionManager extends EventEmitter implements ISelectionManager
       return false;
     }
 
+    return this._areCoordsInSelection(coords, start, end);
+  }
+
+  protected _areCoordsInSelection(coords: [number, number], start: [number, number], end: [number, number]): boolean {
     return (coords[1] > start[1] && coords[1] < end[1]) ||
-        (start[1] === end[1] && coords[1] === start[1] && coords[0] > start[0] && coords[0] < end[0]) ||
-        (start[1] < end[1] && coords[1] === end[1] && coords[0] < end[0]);
+        (start[1] === end[1] && coords[1] === start[1] && coords[0] >= start[0] && coords[0] < end[0]) ||
+        (start[1] < end[1] && coords[1] === end[1] && coords[0] < end[0]) ||
+        (start[1] < end[1] && coords[1] === start[1] && coords[0] >= start[0]);
   }
 
   /**