diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
index 39fadc6e149219771985bfc1d697a47afe27f885..586962f65c2a033d59a240e5daf85ece91859532 100644
--- a/arch/powerpc/kernel/pci_64.c
+++ b/arch/powerpc/kernel/pci_64.c
@@ -560,9 +560,14 @@ long sys_pciconfig_iobase(long which, unsigned long in_bus,
 	 * G5 machines... So when something asks for bus 0 io base
 	 * (bus 0 is HT root), we return the AGP one instead.
 	 */
-	if (machine_is_compatible("MacRISC4"))
-		if (in_bus == 0)
+	if (in_bus == 0 && machine_is_compatible("MacRISC4")) {
+		struct device_node *agp;
+
+		agp = of_find_compatible_node(NULL, NULL, "u3-agp");
+		if (agp)
 			in_bus = 0xf0;
+		of_node_put(agp);
+	}
 
 	/* That syscall isn't quite compatible with PCI domains, but it's
 	 * used on pre-domains setup. We return the first match