diff --git a/src/QBar/Qubes/AdminAPI.hs b/src/QBar/Qubes/AdminAPI.hs
index ae8b08802840761ff4b2abac56546368f0e0c766..7fcac49795f5d7830176cdbd15cef1a0f18d06d2 100644
--- a/src/QBar/Qubes/AdminAPI.hs
+++ b/src/QBar/Qubes/AdminAPI.hs
@@ -30,7 +30,7 @@ data QubesAdminReturn
 
 putLazyByteStringNul :: BL.ByteString -> Put
 putLazyByteStringNul x = do
-  when (0 `BL.elem` x) $ error "string mustn't contain any \\x00 bytes"
+  when (0 `BL.elem` x) $ error "String must not contain any \\x00 bytes"
   putLazyByteString x
   putWord8 0x00