diff --git a/src/doc/book/ffi.md b/src/doc/book/ffi.md
index 983bd46a0c9..f9c50f0399a 100644
--- a/src/doc/book/ffi.md
+++ b/src/doc/book/ffi.md
@@ -635,7 +635,7 @@ void register(void (*f)(void (*)(int), int)) {
 }
 ```
 
-No `tranmsute` required!
+No `transmute` required!
 
 # Calling Rust code from C