diff --git a/macosx.c b/macosx.c
index f5f1944..a0df84e 100644
--- a/macosx.c
+++ b/macosx.c
@@ -63,6 +63,17 @@ SP_PRIV enum sp_return get_port_details(struct sp_port *port)
 		DEBUG_FMT("Found port %s", path);
 
 		IORegistryEntryGetParentEntry(ioport, kIOServicePlane, &ioparent);
+		if ((cf_property=IORegistryEntrySearchCFProperty(ioparent,kIOServicePlane,
+		           CFSTR("IOClass"), kCFAllocatorDefault,
+		           kIORegistryIterateRecursively | kIORegistryIterateParents))) {
+			if (CFStringGetCString(cf_property, class, sizeof(class),
+			                       kCFStringEncodingASCII) &&
+			    strstr(class, "USB")) {
+				DEBUG("Found USB class device");
+				port->transport = SP_TRANSPORT_USB;
+			}
+			CFRelease(cf_property);
+		}
 		if ((cf_property=IORegistryEntrySearchCFProperty(ioparent,kIOServicePlane,
 		           CFSTR("IOProviderClass"), kCFAllocatorDefault,
 		           kIORegistryIterateRecursively | kIORegistryIterateParents))) {