diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c18dd8d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__/
diff --git a/README.md b/README.md
index c0987a4..efb743b 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,8 @@ You need Python 3 and [Requests](http://python-requests.org/). You can install R
 
 Then, copy the script `check_expire` and the file `ianardap.py`to the directory of local plugins.
 
+The use of a cache directory is not mandatory, but highly recommended. It can be either `$XDG_CACHE_HOME/ianardap` or `$HOME/.ianardapcaches` depending on the environment variables set.
+
 ## Icinga configuration
 
 If you use Icinga, here is a possible definition of the command:
@@ -35,6 +37,7 @@ object CheckCommand "expiration" {
       "-v" = { set_if = "$expiration_verbose$" }
   }
 
+  env.XDG_CACHE_HOME = "/var/cache/nagios"
 }
 
 apply Service "expiration" {
@@ -60,6 +63,13 @@ object Host "bortzmeyer-org" {
 }
 ```
 
+If needed, create the cache directory accordingly:
+
+```
+mkdir /var/cache/nagios
+chown nagios: /var/cache/nagios
+```
+
 ## Zabbix configuration
 
 For monitoring systems that do not rely on exit codes but on calculation mechanism based on the metric they receive you can use the `-u` option that will only return the expiration date in unixtime format.
diff --git a/check_expire b/check_expire
index 8e1ab29..7c014dc 100755
--- a/check_expire
+++ b/check_expire
@@ -53,6 +53,8 @@ def usage(msg=None):
         print("")
 
 def details():
+    if database and not database.cachefile:
+        print(" (WARNING: no cache directory used, please set environement variable XDG_CACHE_HOME or HOME.)", end="")
     if verbose:
         print(" RDAP database \"%s\", version %s published on %s, retrieved on %s, RDAP server is %s" % \
               (database.description, database.version, database.publication, database.retrieved, server))
diff --git a/ianardap.py b/ianardap.py
index 473aa56..5bd1796 100755
--- a/ianardap.py
+++ b/ianardap.py
@@ -21,7 +21,8 @@ IANABASES = {"domains": "https://data.iana.org/rdap/dns.json",
              "v6prefixes": "https://data.iana.org/rdap/ipv6.json",
              "as": "https://data.iana.org/rdap/asn.json",
              "objects": "https://data.iana.org/rdap/object-tags.json"}
-CACHE = os.environ["HOME"] + "/.ianardapcaches" 
+CACHE = os.environ["XDG_CACHE_HOME"] + "/ianardap" if "XDG_CACHE_HOME" in os.environ else \
+        (os.environ["HOME"] + "/.ianardapcaches" if "HOME" in os.environ else None)
 MAXAGE = 24 # Hours. Used only if the server no longer gives the information.
 IANATIMEOUT = 10 # Seconds
 MAXTESTS = 3 # Maximum attempts to get the database
@@ -60,28 +61,33 @@ file (see the documentation of the module).
         """
         
         cache_valid = False
-        if not os.path.exists(cachedir):
-            os.mkdir(cachedir)
         self.category = category
-        cachefile = os.path.join(cachedir, category)
-        if pickleformat:
-            self.cachefile = cachefile + ".pickle"
-        else:
-            self.cachefile = cachefile + ".json"
-        self.lockname = self.cachefile + ".lock"
-        self.expirationfile = self.cachefile + ".expires"
+        self.cachefile = None
+        self.lockname = None
+        self.expirationfile = None
+        if cachedir:
+            if not os.path.exists(cachedir):
+                os.mkdir(cachedir)
+            cachefile = os.path.join(cachedir, category)
+            if pickleformat:
+                self.cachefile = cachefile + ".pickle"
+            else:
+                self.cachefile = cachefile + ".json"
+            self.lockname = self.cachefile + ".lock"
+            self.expirationfile = self.cachefile + ".expires"
         if maxage is not None:
-            with open(self.expirationfile, 'w'):
-                self.expirationtime = time.mktime((datetime.datetime.now() + \
-                                                  datetime.timedelta(hours=maxage)).timetuple())
-                os.utime(self.expirationfile,
-                         times = (self.expirationtime, self.expirationtime))
+            self.expirationtime = time.mktime((datetime.datetime.now() + \
+                                              datetime.timedelta(hours=maxage)).timetuple())
+            if self.expirationfile:
+                with open(self.expirationfile, 'w'):
+                    os.utime(self.expirationfile,
+                             times = (self.expirationtime, self.expirationtime))
         loaded = False
         tests = 0
         errmsg = "No error"
         while not loaded and tests < MAXTESTS:
             self.lock()
-            if os.path.exists(self.cachefile) and \
+            if self.cachefile and os.path.exists(self.cachefile) and \
                (pathlib.Path(self.expirationfile).exists() and \
                 datetime.datetime.fromtimestamp(os.path.getmtime(self.expirationfile)) > \
                 datetime.datetime.now()):
@@ -139,9 +145,10 @@ file (see the documentation of the module).
                 try:
                     content = response.content
                     database = json.loads(content)
-                    with open(self.expirationfile, 'w'):
-                        os.utime(self.expirationfile,
-                                 times = (self.expirationtime, self.expirationtime))
+                    if self.expirationfile:
+                        with open(self.expirationfile, 'w'):
+                            os.utime(self.expirationfile,
+                                     times = (self.expirationtime, self.expirationtime))
                 except json.decoder.JSONDecodeError:
                     tests += 1
                     errmsg = "Invalid JSON retrieved from %s" % IANABASE
@@ -173,7 +180,7 @@ file (see the documentation of the module).
         else: # IP addresses will be complicated, because of the
               # longest prefix rule.
             raise Exception("Unsupported category %s" % self.category)
-        if not cache_valid:
+        if self.cachefile and not cache_valid:
             self.lock()
             cache = open(self.cachefile, "wb")
             if pickleformat:
@@ -184,12 +191,14 @@ file (see the documentation of the module).
             self.unlock()
         
     def lock(self):
-        self.lockhandle = open(self.lockname, 'w')
-        fcntl.lockf(self.lockhandle, fcntl.LOCK_EX)
+        if self.lockname:
+            self.lockhandle = open(self.lockname, 'w')
+            fcntl.lockf(self.lockhandle, fcntl.LOCK_EX)
 
     def unlock(self):
-        fcntl.lockf(self.lockhandle, fcntl.LOCK_UN)
-        self.lockhandle.close()
+        if self.lockname:
+            fcntl.lockf(self.lockhandle, fcntl.LOCK_UN)
+            self.lockhandle.close()
 
     def find(self, id):
         """Get the RDAP server(s), as an array, for a given identifier. None
diff --git a/test_ianardap.py b/test_ianardap.py
index 0dfdb88..f2910ec 100644
--- a/test_ianardap.py
+++ b/test_ianardap.py
@@ -29,8 +29,9 @@ def test_refresh():
     # Force a resfresh
     database = ianardap.IanaRDAPDatabase(maxage=0)
     assert (database.retrieved > (datetime.datetime.now() - datetime.timedelta(minutes=1))) and \
+        ((not database.cachefile) or \
         (datetime.datetime.fromtimestamp(os.path.getmtime(database.cachefile)) > \
-        (datetime.datetime.now() - datetime.timedelta(minutes=1)))
+        (datetime.datetime.now() - datetime.timedelta(minutes=1))))
 
 def test_find_exists():
     database = ianardap.IanaRDAPDatabase()