diff --git a/src/SelectionManager.ts b/src/SelectionManager.ts
index c01d7b6d..a639a75e 100644
--- a/src/SelectionManager.ts
+++ b/src/SelectionManager.ts
@@ -258,8 +258,8 @@ export class SelectionManager extends EventEmitter implements ISelectionManager
     }
 
     return (start[1] < coords[1] && end[1] > coords[1]) ||
-        (start[1] === coords[1] && coords[0] > start[0]) ||
-        (end[1] === coords[1] && coords[0] < end[0]);
+        (start[1] === end[1] && start[1] === coords[1] && coords[0] > start[0] && coords[0] < end[0]) ||
+        (start[1] < end[1] && end[1] === coords[1] && coords[0] < end[0]);
   }
 
   /**