diff --git a/devsupApp/src/dbdset.c b/devsupApp/src/dbdset.c
index deeab2a..f2987a3 100644
--- a/devsupApp/src/dbdset.c
+++ b/devsupApp/src/dbdset.c
@@ -122,7 +122,7 @@ static int allow_ioscan(pyDevice *priv)
 
 static void release_ioscan(pyDevice *priv)
 {
-    if(priv->scanobj && PyObject_HasAttrString(priv->scanobj, "release")) {
+    if(priv->scanobj && PyCallable_Check(priv->scanobj)) {
         PyObject *ret = PyObject_CallFunction(priv->scanobj, "O", priv->pyrecord);
         if(ret)
             Py_DECREF(ret);
diff --git a/python/devsup/interfaces.py b/python/devsup/interfaces.py
index 5be1b0a..ec5c8c9 100644
--- a/python/devsup/interfaces.py
+++ b/python/devsup/interfaces.py
@@ -11,6 +11,11 @@ class DeviceSupport(Interface):
     def allowScan(record):
         """Return True to allow SCAN='I/O Intr'
         or False to prevent this.
+        
+        If a callable object is returned then if
+        will be invoked when I/O Intr scanning
+        is disabled.  A Record instance is passed
+        as the first (and only) argument.
         """
 
     def process(record, reason):