diff --git a/collects/file/md5.ss b/collects/file/md5.ss
index f0701f3e00..f05b5389be 100644
--- a/collects/file/md5.ss
+++ b/collects/file/md5.ss
@@ -76,7 +76,7 @@
 
 (require (for-syntax scheme/base))
 
-;;; Word aritmetic (32 bit)
+;;; Word arithmetic (32 bit)
 ;; Terminology
 ;;    word:  32 bit unsigned integer
 ;;    byte:   8 bit unsigned integer