diff --git a/costs/src/context.rs b/costs/src/context.rs
index 8224cb88..d661e3a1 100644
--- a/costs/src/context.rs
+++ b/costs/src/context.rs
@@ -179,7 +179,7 @@ impl<T> CostsExt for T {}
 /// 1. Early termination on error;
 /// 2. Because of 1, `Result` is removed from the equation;
 /// 3. `CostContext` is removed too because it is added to external cost
-/// accumulator;
+///    accumulator;
 /// 4. Early termination uses external cost accumulator so previous costs won't
 ///    be lost.
 #[macro_export]