diff --git a/sys/x86/iommu/amd_drv.c b/sys/x86/iommu/amd_drv.c
index 2ab0213925e..72aae58334f 100644
--- a/sys/x86/iommu/amd_drv.c
+++ b/sys/x86/iommu/amd_drv.c
@@ -176,7 +176,6 @@ ivrs_lookup_ivhd_0x40(ACPI_IVRS_HARDWARE2 *h2, void *arg)
 		return (false);
 
 	ildp->sc->unit_dom = h2->PciSegmentGroup;
-	ildp->sc->iommu.unit = ivrs_info_to_unit_id(h2->Info);
 	ildp->sc->efr = h2->EfrRegisterImage;
 	return (true);
 }
@@ -194,7 +193,6 @@ ivrs_lookup_ivhd_0x10(ACPI_IVRS_HARDWARE1 *h1, void *arg)
 		return (false);
 
 	ildp->sc->unit_dom = h1->PciSegmentGroup;
-	ildp->sc->iommu.unit = ivrs_info_to_unit_id(h1->Info);
 	return (true);
 }
 
@@ -456,6 +454,7 @@ amdiommu_attach(device_t dev)
 	bool res;
 
 	sc = device_get_softc(dev);
+	sc->iommu.unit = device_get_unit(dev);
 	sc->iommu.dev = dev;
 
 	error = pci_find_cap(dev, PCIY_SECDEV, &sc->seccap_reg);