diff --git a/source/lib/res/res.cpp b/source/lib/res/res.cpp
index a4b050a23c..612fb62e06 100755
--- a/source/lib/res/res.cpp
+++ b/source/lib/res/res.cpp
@@ -25,7 +25,7 @@ static bool initialized;
 
 // path: portable and relative, must add current directory and convert to native
 // better to use a cached string from rel_chdir - secure
-int res_watch_dir(const char* const path, uint* const reqnum)
+int res_watch_dir(const char* const path, uintptr_t* const watch)
 {
 	if(!initialized)
 	{
@@ -41,12 +41,12 @@ int res_watch_dir(const char* const path, uint* const reqnum)
 	if(FAMMonitorDirectory(&fc, n_full_path, &req, (void*)0) < 0)
 		return -1;	// no way of getting error?
 
-	*reqnum = req.reqnum;
+	*watch = req.reqnum;
 	return 0;
 }
 
 
-int res_cancel_watch(const uint reqnum)
+int res_cancel_watch(const uint watch)
 {
 	if(!initialized)
 	{
@@ -55,7 +55,7 @@ int res_cancel_watch(const uint reqnum)
 	}
 
 	FAMRequest req;
-	req.reqnum = reqnum;
+	req.reqnum = watch;
 	return FAMCancelMonitor(&fc, &req);
 }
 
diff --git a/source/lib/res/res.h b/source/lib/res/res.h
index 7247133751..6bd19b406d 100755
--- a/source/lib/res/res.h
+++ b/source/lib/res/res.h
@@ -13,8 +13,8 @@ extern int res_reload(const char* fn);
 // (wfam limitation)
 
 
-extern int res_watch_dir(const char* const path, uint* const reqnum);
+extern int res_watch_dir(const char* const path, uintptr_t* const watch);
 
-extern int res_cancel_watch(const uint reqnum);
+extern int res_cancel_watch(const uintptr_t watch);
 
 extern int res_reload_changed_files();
diff --git a/source/lib/res/vfs.cpp b/source/lib/res/vfs.cpp
index ca6a7756ff..80fa815abc 100755
--- a/source/lib/res/vfs.cpp
+++ b/source/lib/res/vfs.cpp
@@ -40,11 +40,15 @@
 
 
 // we add/cancel directory watches from the VFS mount code for convenience -
-// it iterates through all subdirectories anyway (the watch code would need
-// to do this, because FAM can't monitor a directory subtree) and provides
-// storage for the FAM request number.
-// define to disable that - removes request number from struct Dir,
+// it iterates through all subdirectories anyway (*) and provides storage for
+// a key to identify the watch (obviates separate Dir -> watch mapping).
+//
+// define this to strip out that code - removes .watch from struct Dir,
 // and calls to res_watch_dir / res_cancel_watch.
+//
+// *: the add_watch code would need to iterate through subdirs and watch
+//    each one, because the monitor API (e.g. FAM) may only be able to
+//    watch single directories, instead of a whole subdirectory tree.
 #undef NO_DIR_WATCH
 
 
@@ -256,7 +260,7 @@ typedef SubDirs::iterator SubDirIt;
 struct Dir
 {
 #ifndef NO_DIR_WATCH
-	uint watch_reqnum;
+	uintptr_t watch;
 #endif
 
 	int add_file(const char* name, const FileLoc* loc);
@@ -351,7 +355,7 @@ void Dir::clearR()
 	files.clear();
 
 #ifndef NO_DIR_WATCH
-	res_cancel_watch(watch_reqnum);
+	res_cancel_watch(watch);
 #endif
 }
 
@@ -524,7 +528,7 @@ static int tree_add_dirR(Dir* const dir, const char* const f_path, const FileLoc
 	file_enum(f_path, add_dirent_cb, (uintptr_t)&params);
 
 #ifndef NO_DIR_WATCH
-	res_watch_dir(f_path, &dir->watch_reqnum);
+	res_watch_dir(f_path, &dir->watch);
 #endif
 
 	for(SubDirIt it = dir->subdirs.begin(); it != dir->subdirs.end(); ++it)