Index: dll/win32/msi/action.c
===================================================================
--- dll/win32/msi/action.c	(revision 71329)
+++ dll/win32/msi/action.c	(working copy)
@@ -4770,9 +4770,9 @@
 static void register_dll( const WCHAR *dll, BOOL unregister )
 {
     static const WCHAR regW[] =
-        {'r','e','g','s','v','r','3','2','.','e','x','e',' ','\"','%','s','\"',0};
+        {'r','e','g','s','v','r','3','2','.','e','x','e',' ','/','s',' ','\"','%','s','\"',0};
     static const WCHAR unregW[] =
-        {'r','e','g','s','v','r','3','2','.','e','x','e',' ','/','u',' ','\"','%','s','\"',0};
+        {'r','e','g','s','v','r','3','2','.','e','x','e',' ','/','s',' ','/','u',' ','\"','%','s','\"',0};
     PROCESS_INFORMATION pi;
     STARTUPINFOW si;
     WCHAR *cmd;