diff --git a/sys/dev/cxgbe/t4_iov.c b/sys/dev/cxgbe/t4_iov.c
--- a/sys/dev/cxgbe/t4_iov.c
+++ b/sys/dev/cxgbe/t4_iov.c
@@ -194,6 +194,7 @@
 {
 	struct t4iov_softc *sc;
 	uint32_t pl_rev, whoami;
+	int error;
 
 	sc = device_get_softc(dev);
 	sc->sc_dev = dev;
@@ -217,10 +218,18 @@
 
 	sc->sc_main = pci_find_dbsf(pci_get_domain(dev), pci_get_bus(dev),
 	    pci_get_slot(dev), 4);
-	if (sc->sc_main == NULL)
+	if (sc->sc_main == NULL) {
+		bus_release_resource(dev, SYS_RES_MEMORY, sc->regs_rid,
+		    sc->regs_res);
 		return (ENXIO);
-	if (T4_IS_MAIN_READY(sc->sc_main) == 0)
-		return (t4iov_attach_child(dev));
+	}
+	if (T4_IS_MAIN_READY(sc->sc_main) == 0) {
+		error = t4iov_attach_child(dev);
+		if (error != 0)
+			bus_release_resource(dev, SYS_RES_MEMORY, sc->regs_rid,
+			    sc->regs_res);
+		return (error);
+	}
 	return (0);
 }