diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
index f86a40aa30..516ebae952 100644
--- a/hw/i386/amd_iommu.c
+++ b/hw/i386/amd_iommu.c
@@ -21,6 +21,7 @@
  */
 #include "qemu/osdep.h"
 #include "hw/i386/amd_iommu.h"
+#include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "trace.h"
 
@@ -1137,7 +1138,19 @@ static void amdvi_realize(DeviceState *dev, Error **err)
     int ret = 0;
     AMDVIState *s = AMD_IOMMU_DEVICE(dev);
     X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(dev);
-    PCIBus *bus = PC_MACHINE(qdev_get_machine())->bus;
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    PCMachineState *pcms =
+        PC_MACHINE(object_dynamic_cast(OBJECT(ms), TYPE_PC_MACHINE));
+    PCIBus *bus;
+
+    if (!pcms) {
+        error_setg(err, "Machine-type '%s' not supported by amd-iommu",
+                   mc->name);
+        return;
+    }
+
+    bus = pcms->bus;
     s->iotlb = g_hash_table_new_full(amdvi_uint64_hash,
                                      amdvi_uint64_equal, g_free, g_free);
 
diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 02f047c8e3..a12b1761f5 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -2969,11 +2969,21 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
 
 static void vtd_realize(DeviceState *dev, Error **errp)
 {
-    PCMachineState *pcms = PC_MACHINE(qdev_get_machine());
-    PCIBus *bus = pcms->bus;
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    PCMachineState *pcms =
+        PC_MACHINE(object_dynamic_cast(OBJECT(ms), TYPE_PC_MACHINE));
+    PCIBus *bus;
     IntelIOMMUState *s = INTEL_IOMMU_DEVICE(dev);
     X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(dev);
 
+    if (!pcms) {
+        error_setg(errp, "Machine-type '%s' not supported by intel-iommu",
+                   mc->name);
+        return;
+    }
+
+    bus = pcms->bus;
     VTD_DPRINTF(GENERAL, "");
     x86_iommu->type = TYPE_INTEL;