diff --git a/runtime/doc/diff.txt b/runtime/doc/diff.txt
index d72f37e..fad6801 100644
--- a/runtime/doc/diff.txt
+++ b/runtime/doc/diff.txt
@@ -382,13 +382,13 @@
 	function MyDiff()
 	   let opt = ""
 	   if &diffopt =~ "icase"
-	     let opt = opt . "-i "
+	     let opt = opt .. "-i "
 	   endif
 	   if &diffopt =~ "iwhite"
-	     let opt = opt . "-b "
+	     let opt = opt .. "-b "
 	   endif
-	   silent execute "!diff -a --binary " . opt . v:fname_in . " " . v:fname_new .
-		\  " > " . v:fname_out
+	   silent execute "!diff -a --binary " .. opt .. v:fname_in .. " " .. v:fname_new ..
+		\  " > " .. v:fname_out
 	   redraw!
 	endfunction
 
@@ -445,8 +445,8 @@
 
 	set patchexpr=MyPatch()
 	function MyPatch()
-	   :call system("patch -o " . v:fname_out . " " . v:fname_in .
-	   \  " < " . v:fname_diff)
+	   :call system("patch -o " .. v:fname_out .. " " .. v:fname_in ..
+	   \  " < " .. v:fname_diff)
 	endfunction
 
 Make sure that using the "patch" program doesn't have unwanted side effects.