diff --git a/roaring/src/lib.rs b/roaring/src/lib.rs
index f6c4453b..d66f15f5 100644
--- a/roaring/src/lib.rs
+++ b/roaring/src/lib.rs
@@ -43,6 +43,9 @@ impl fmt::Display for IntegerTooSmall {
     }
 }
 
+#[cfg(feature = "std")]
+impl std::error::Error for IntegerTooSmall {}
+
 /// An error type that is returned when an iterator isn't sorted.
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct NonSortedIntegers {