diff --git a/src/locks/lockhandler.py b/src/locks/lockhandler.py
index 5262fb423d..1fc39fb1bc 100644
--- a/src/locks/lockhandler.py
+++ b/src/locks/lockhandler.py
@@ -211,7 +211,9 @@ class LockHandler(object):
 
             # parse the lock functions and separators
             funclist = _RE_FUNCS.findall(rhs)
-            evalstring = rhs.replace('AND','and').replace('OR','or').replace('NOT','not')
+            evalstring = rhs
+            for pattern in ('AND', 'OR', 'NOT'):
+                evalstring = re.sub(r"\b%s\b" % pattern, pattern.lower(), evalstring)
             nfuncs = len(funclist)
             for funcstring in funclist:
                 funcname, rest = (part.strip().strip(')') for part in funcstring.split('(', 1))
@@ -226,7 +228,7 @@ class LockHandler(object):
             if len(lock_funcs) < nfuncs:
                 continue
             try:
-                # purge the eval string of any superfluos items, then test it
+                # purge the eval string of any superfluous items, then test it
                 evalstring = " ".join(_RE_OK.findall(evalstring))
                 eval(evalstring % tuple(True for func in funclist), {}, {})
             except Exception: