diff --git a/src/book/mod.rs b/src/book/mod.rs
index 46ad5a9c..0723578f 100644
--- a/src/book/mod.rs
+++ b/src/book/mod.rs
@@ -294,7 +294,7 @@ impl MDBook {
             }
         }
         if failed {
-            bail!("One of more tests failed");
+            bail!("One or more tests failed");
         }
         Ok(())
     }