diff --git a/src/bluetooth.c b/src/bluetooth.c
index 282a31a..e6fafd5 100644
--- a/src/bluetooth.c
+++ b/src/bluetooth.c
@@ -79,7 +79,7 @@ static dc_status_t dc_bluetooth_iterator_free (dc_iterator_t *iterator);
 
 typedef struct dc_bluetooth_iterator_t {
 	dc_iterator_t base;
-	dc_filter_t filter;
+	dc_descriptor_t *descriptor;
 #ifdef _WIN32
 	HANDLE hLookup;
 #else
@@ -376,7 +376,7 @@ dc_bluetooth_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descri
 	iterator->count = ndevices;
 	iterator->current = 0;
 #endif
-	iterator->filter = dc_descriptor_get_filter (descriptor);
+	iterator->descriptor = descriptor;
 
 	*out = (dc_iterator_t *) iterator;
 
@@ -456,7 +456,7 @@ dc_bluetooth_iterator_next (dc_iterator_t *abstract, void *out)
 		INFO (abstract->context, "Discover: address=" DC_ADDRESS_FORMAT ", name=%s",
 			address, name ? name : "");
 
-		if (iterator->filter && !iterator->filter (DC_TRANSPORT_BLUETOOTH, name)) {
+		if (!dc_descriptor_filter (iterator->descriptor, DC_TRANSPORT_BLUETOOTH, name)) {
 			continue;
 		}
 
diff --git a/src/descriptor-private.h b/src/descriptor-private.h
index 5023f7f..06c2980 100644
--- a/src/descriptor-private.h
+++ b/src/descriptor-private.h
@@ -33,10 +33,8 @@ typedef struct dc_usb_desc_t {
 	unsigned short pid;
 } dc_usb_desc_t;
 
-typedef int (*dc_filter_t) (dc_transport_t transport, const void *userdata);
-
-dc_filter_t
-dc_descriptor_get_filter (dc_descriptor_t *descriptor);
+int
+dc_descriptor_filter (dc_descriptor_t *descriptor, dc_transport_t transport, const void *userdata);
 
 #ifdef __cplusplus
 }
diff --git a/src/descriptor.c b/src/descriptor.c
index 7f2de39..183d3d5 100644
--- a/src/descriptor.c
+++ b/src/descriptor.c
@@ -40,6 +40,8 @@
 
 typedef int (*dc_match_t)(const void *, const void *);
 
+typedef int (*dc_filter_t) (dc_transport_t transport, const void *userdata);
+
 static int dc_filter_uwatec (dc_transport_t transport, const void *userdata);
 static int dc_filter_suunto (dc_transport_t transport, const void *userdata);
 static int dc_filter_shearwater (dc_transport_t transport, const void *userdata);
@@ -745,11 +747,11 @@ dc_descriptor_get_transports (dc_descriptor_t *descriptor)
 	return descriptor->transports;
 }
 
-dc_filter_t
-dc_descriptor_get_filter (dc_descriptor_t *descriptor)
+int
+dc_descriptor_filter (dc_descriptor_t *descriptor, dc_transport_t transport, const void *userdata)
 {
-	if (descriptor == NULL)
-		return NULL;
+	if (descriptor == NULL || descriptor->filter == NULL)
+		return 1;
 
-	return descriptor->filter;
+	return descriptor->filter (transport, userdata);
 }
diff --git a/src/irda.c b/src/irda.c
index 214e39f..89b7e50 100644
--- a/src/irda.c
+++ b/src/irda.c
@@ -212,8 +212,6 @@ dc_irda_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descriptor_
 	S_CLOSE (fd);
 	dc_socket_exit (context);
 
-	dc_filter_t filter = dc_descriptor_get_filter (descriptor);
-
 	unsigned int count = 0;
 #ifdef _WIN32
 	for (size_t i = 0; i < list->numDevice; ++i) {
@@ -233,7 +231,7 @@ dc_irda_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descriptor_
 		INFO (context, "Discover: address=%08x, name=%s, charset=%02x, hints=%04x",
 			address, name, charset, hints);
 
-		if (filter && !filter (DC_TRANSPORT_IRDA, name)) {
+		if (!dc_descriptor_filter (descriptor, DC_TRANSPORT_IRDA, name)) {
 			continue;
 		}
 
diff --git a/src/serial_posix.c b/src/serial_posix.c
index 897b428..cca501e 100644
--- a/src/serial_posix.c
+++ b/src/serial_posix.c
@@ -88,7 +88,7 @@ struct dc_serial_device_t {
 
 typedef struct dc_serial_iterator_t {
 	dc_iterator_t base;
-	dc_filter_t filter;
+	dc_descriptor_t *descriptor;
 	DIR *dp;
 } dc_serial_iterator_t;
 
@@ -189,7 +189,7 @@ dc_serial_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descripto
 		goto error_free;
 	}
 
-	iterator->filter = dc_descriptor_get_filter (descriptor);
+	iterator->descriptor = descriptor;
 
 	*out = (dc_iterator_t *) iterator;
 
@@ -230,7 +230,7 @@ dc_serial_iterator_next (dc_iterator_t *abstract, void *out)
 				return DC_STATUS_NOMEMORY;
 			}
 
-			if (iterator->filter && !iterator->filter (DC_TRANSPORT_SERIAL, filename)) {
+			if (!dc_descriptor_filter (iterator->descriptor, DC_TRANSPORT_SERIAL, filename)) {
 				continue;
 			}
 
diff --git a/src/serial_win32.c b/src/serial_win32.c
index 3cb10ff..b51aafd 100644
--- a/src/serial_win32.c
+++ b/src/serial_win32.c
@@ -57,7 +57,7 @@ struct dc_serial_device_t {
 
 typedef struct dc_serial_iterator_t {
 	dc_iterator_t base;
-	dc_filter_t filter;
+	dc_descriptor_t *descriptor;
 	HKEY hKey;
 	DWORD count;
 	DWORD current;
@@ -180,7 +180,7 @@ dc_serial_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descripto
 		}
 	}
 
-	iterator->filter = dc_descriptor_get_filter (descriptor);
+	iterator->descriptor = descriptor;
 	iterator->hKey = hKey;
 	iterator->count = count;
 	iterator->current = 0;
@@ -226,7 +226,7 @@ dc_serial_iterator_next (dc_iterator_t *abstract, void *out)
 		// Null terminate the string.
 		data[data_len] = 0;
 
-		if (iterator->filter && !iterator->filter (DC_TRANSPORT_SERIAL, data)) {
+		if (!dc_descriptor_filter (iterator->descriptor, DC_TRANSPORT_SERIAL, data)) {
 			continue;
 		}
 
diff --git a/src/usbhid.c b/src/usbhid.c
index e26d42b..9ed6648 100644
--- a/src/usbhid.c
+++ b/src/usbhid.c
@@ -102,7 +102,7 @@ static dc_status_t dc_usbhid_close (dc_iostream_t *iostream);
 
 typedef struct dc_usbhid_iterator_t {
 	dc_iterator_t base;
-	dc_filter_t filter;
+	dc_descriptor_t *descriptor;
 	dc_usbhid_session_t *session;
 #if defined(USE_LIBUSB)
 	struct libusb_device **devices;
@@ -398,7 +398,7 @@ dc_usbhid_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descripto
 	iterator->devices = devices;
 	iterator->current = devices;
 #endif
-	iterator->filter = dc_descriptor_get_filter (descriptor);
+	iterator->descriptor = descriptor;
 
 	*out = (dc_iterator_t *) iterator;
 
@@ -435,7 +435,7 @@ dc_usbhid_iterator_next (dc_iterator_t *abstract, void *out)
 		}
 
 		dc_usb_desc_t usb = {dev.idVendor, dev.idProduct};
-		if (iterator->filter && !iterator->filter (DC_TRANSPORT_USBHID, &usb)) {
+		if (!dc_descriptor_filter (iterator->descriptor, DC_TRANSPORT_USBHID, &usb)) {
 			continue;
 		}
 
@@ -518,7 +518,7 @@ dc_usbhid_iterator_next (dc_iterator_t *abstract, void *out)
 		iterator->current = current->next;
 
 		dc_usb_desc_t usb = {current->vendor_id, current->product_id};
-		if (iterator->filter && !iterator->filter (DC_TRANSPORT_USBHID, &usb)) {
+		if (!dc_descriptor_filter (iterator->descriptor, DC_TRANSPORT_USBHID, &usb)) {
 			continue;
 		}