diff --git a/src/slope_func.h b/src/slope_func.h
--- a/src/slope_func.h
+++ b/src/slope_func.h
@@ -239,7 +239,7 @@ static inline DiagDirection GetInclinedS
 }
 
 /**
- * Returns the slope, that is inclined in a specific direction.
+ * Returns the slope that is inclined in a specific direction.
  *
  * @param dir A #DiagDirection
  * @return The #Slope that goes up in direction dir.