--- a/moz.configure
+++ b/moz.configure
@@ -360,16 +360,29 @@ check_prog('GMAKE', possible_makes)
 def tup_progs(build_backends):
     for backend in build_backends:
         if 'Tup' in backend:
             return ['tup']
     return None
 
 tup = check_prog('TUP', tup_progs)
 
+# watchman detection
+# ==============================================================
+
+watchman = check_prog('WATCHMAN', ('watchman',), allow_missing=True)
+
+@depends_if(watchman)
+@checking('for watchman version')
+@imports('json')
+def watchman_version(watchman):
+    out = check_cmd_output(watchman, 'version')
+    res = json.loads(out)
+    return Version(res['version'])
+
 # Miscellaneous programs
 # ==============================================================
 check_prog('DOXYGEN', ('doxygen',), allow_missing=True)
 check_prog('XARGS', ('xargs',))
 
 @depends(target)
 def extra_programs(target):
     if target.kernel == 'Darwin':