diff --git a/helix-core/src/movement.rs b/helix-core/src/movement.rs
index d6745fff..297911ae 100644
--- a/helix-core/src/movement.rs
+++ b/helix-core/src/movement.rs
@@ -199,7 +199,7 @@ fn categorize(ch: char) -> Category {
     } else if ch.is_ascii_punctuation() {
         Category::Punctuation
     } else {
-        unreachable!()
+        unreachable!("unknown '{}' character category", ch)
     }
 }