diff --git a/sys/src/9/pc/trap.c b/sys/src/9/pc/trap.c
index 0593784fb..65915e06c 100644
--- a/sys/src/9/pc/trap.c
+++ b/sys/src/9/pc/trap.c
@@ -40,6 +40,12 @@ intrenable(int irq, void (*f)(Ureg*, void*), void* a, int tbdf, char *name)
 		return;
 	}
 
+	if(tbdf != BUSUNKNOWN && (irq == 0xff || irq == 0)){
+		print("intrenable: got unassigned irq %d, tbdf 0x%uX for %s\n",
+			irq, tbdf, name);
+		irq = -1;
+	}
+
 	if((v = xalloc(sizeof(Vctl))) == nil)
 		panic("intrenable: out of memory");
 	v->isintr = 1;
diff --git a/sys/src/9/pc/usbehcipc.c b/sys/src/9/pc/usbehcipc.c
index b1394c039..20b09e3f9 100644
--- a/sys/src/9/pc/usbehcipc.c
+++ b/sys/src/9/pc/usbehcipc.c
@@ -172,10 +172,6 @@ scanpci(void)
 				p->vid, p->did);
 			continue;
 		}
-		if(p->intl == 0xff || p->intl == 0) {
-			print("usbehci: no irq assigned for port %#lux\n", io);
-			continue;
-		}
 		dprint("usbehci: %#x %#x: port %#lux size %#x irq %d\n",
 			p->vid, p->did, io, p->mem[0].size, p->intl);
 
diff --git a/sys/src/9/pc/usbohci.c b/sys/src/9/pc/usbohci.c
index eee329238..522a8df39 100644
--- a/sys/src/9/pc/usbohci.c
+++ b/sys/src/9/pc/usbohci.c
@@ -2382,10 +2382,6 @@ scanpci(void)
 			print("usbohci: failed to map registers\n");
 			continue;
 		}
-		if(p->intl == 0xFF || p->intl == 0) {
-			print("usbohci: no irq assigned for port %#lux\n", mem);
-			continue;
-		}
 
 		ctlr = malloc(sizeof(Ctlr));
 		if(ctlr == nil){
diff --git a/sys/src/9/pc/usbuhci.c b/sys/src/9/pc/usbuhci.c
index 00db8d7bc..e5d599c21 100644
--- a/sys/src/9/pc/usbuhci.c
+++ b/sys/src/9/pc/usbuhci.c
@@ -2137,10 +2137,6 @@ scanpci(void)
 			print("usbuhci: port %#ux in use\n", io);
 			continue;
 		}
-		if(p->intl == 0xFF || p->intl == 0){
-			print("usbuhci: no irq assigned for port %#ux\n", io);
-			continue;
-		}
 
 		dprint("uhci: %#x %#x: port %#ux size %#x irq %d\n",
 			p->vid, p->did, io, p->mem[4].size, p->intl);