diff --git a/include/hw/nubus/mac-nubus-bridge.h b/include/hw/nubus/mac-nubus-bridge.h
index 36aa098dd4bf..118d67267dd5 100644
--- a/include/hw/nubus/mac-nubus-bridge.h
+++ b/include/hw/nubus/mac-nubus-bridge.h
@@ -12,6 +12,10 @@
 #include "hw/nubus/nubus.h"
 #include "qom/object.h"
 
+#define MAC_NUBUS_FIRST_SLOT 0x9
+#define MAC_NUBUS_LAST_SLOT  0xe
+#define MAC_NUBUS_SLOT_NB    (MAC_NUBUS_LAST_SLOT - MAC_NUBUS_FIRST_SLOT + 1)
+
 #define TYPE_MAC_NUBUS_BRIDGE "mac-nubus-bridge"
 OBJECT_DECLARE_SIMPLE_TYPE(MacNubusState, MAC_NUBUS_BRIDGE)
 
diff --git a/include/hw/nubus/nubus.h b/include/hw/nubus/nubus.h
index 89b0976aaa3d..3eea2952d553 100644
--- a/include/hw/nubus/nubus.h
+++ b/include/hw/nubus/nubus.h
@@ -14,13 +14,12 @@
 #include "qom/object.h"
 
 #define NUBUS_SUPER_SLOT_SIZE 0x10000000U
-#define NUBUS_SUPER_SLOT_NB   0x9
+#define NUBUS_SUPER_SLOT_NB   0xe
 
 #define NUBUS_SLOT_SIZE       0x01000000
-#define NUBUS_SLOT_NB         0xF
-
-#define NUBUS_FIRST_SLOT      0x9
-#define NUBUS_LAST_SLOT       0xF
+#define NUBUS_FIRST_SLOT      0x0
+#define NUBUS_LAST_SLOT       0xf
+#define NUBUS_SLOT_NB         (NUBUS_LAST_SLOT - NUBUS_FIRST_SLOT + 1)
 
 #define TYPE_NUBUS_DEVICE "nubus-device"
 OBJECT_DECLARE_SIMPLE_TYPE(NubusDevice, NUBUS_DEVICE)
@@ -36,13 +35,13 @@ struct NubusBus {
     MemoryRegion super_slot_io;
     MemoryRegion slot_io;
 
-    int current_slot;
+    uint16_t slot_available_mask;
 };
 
 struct NubusDevice {
     DeviceState qdev;
 
-    int slot;
+    int32_t slot;
     MemoryRegion super_slot_mem;
     MemoryRegion slot_mem;
 
diff --git a/hw/nubus/mac-nubus-bridge.c b/hw/nubus/mac-nubus-bridge.c
index 7c329300b82c..3f075789e9b3 100644
--- a/hw/nubus/mac-nubus-bridge.c
+++ b/hw/nubus/mac-nubus-bridge.c
@@ -18,6 +18,10 @@ static void mac_nubus_bridge_init(Object *obj)
 
     s->bus = NUBUS_BUS(qbus_create(TYPE_NUBUS_BUS, DEVICE(s), NULL));
 
+    /* Macintosh only has slots 0x9 to 0xe available */
+    s->bus->slot_available_mask = MAKE_64BIT_MASK(MAC_NUBUS_FIRST_SLOT,
+                                                  MAC_NUBUS_SLOT_NB);
+
     sysbus_init_mmio(sbd, &s->bus->super_slot_io);
     sysbus_init_mmio(sbd, &s->bus->slot_io);
 }
diff --git a/hw/nubus/nubus-bus.c b/hw/nubus/nubus-bus.c
index f4410803fffe..3cd75348646b 100644
--- a/hw/nubus/nubus-bus.c
+++ b/hw/nubus/nubus-bus.c
@@ -86,13 +86,14 @@ static void nubus_init(Object *obj)
 
     memory_region_init_io(&nubus->super_slot_io, obj, &nubus_super_slot_ops,
                           nubus, "nubus-super-slots",
-                          NUBUS_SUPER_SLOT_NB * NUBUS_SUPER_SLOT_SIZE);
+                          (NUBUS_SUPER_SLOT_NB + 1) * NUBUS_SUPER_SLOT_SIZE);
 
     memory_region_init_io(&nubus->slot_io, obj, &nubus_slot_ops,
                           nubus, "nubus-slots",
                           NUBUS_SLOT_NB * NUBUS_SLOT_SIZE);
 
-    nubus->current_slot = NUBUS_FIRST_SLOT;
+    nubus->slot_available_mask = MAKE_64BIT_MASK(NUBUS_FIRST_SLOT,
+                                                 NUBUS_SLOT_NB);
 }
 
 static void nubus_class_init(ObjectClass *oc, void *data)
diff --git a/hw/nubus/nubus-device.c b/hw/nubus/nubus-device.c
index 4e23df1280f9..2e96d6b4fc39 100644
--- a/hw/nubus/nubus-device.c
+++ b/hw/nubus/nubus-device.c
@@ -161,13 +161,26 @@ static void nubus_device_realize(DeviceState *dev, Error **errp)
     char *name;
     hwaddr slot_offset;
 
-    if (nubus->current_slot < NUBUS_FIRST_SLOT ||
-            nubus->current_slot > NUBUS_LAST_SLOT) {
-        error_setg(errp, "Cannot register nubus card, not enough slots");
-        return;
+    if (nd->slot == -1) {
+        /* No slot specified, find first available free slot */
+        int s = ctz32(nubus->slot_available_mask);
+        if (s != 32) {
+            nd->slot = s;
+        } else {
+            error_setg(errp, "Cannot register nubus card, no free slot "
+                             "available");
+            return;
+        }
+    } else {
+        /* Slot specified, make sure the slot is available */
+        if (!(nubus->slot_available_mask & BIT(nd->slot))) {
+            error_setg(errp, "Cannot register nubus card, slot %d is "
+                             "unavailable or already occupied", nd->slot);
+            return;
+        }
     }
 
-    nd->slot = nubus->current_slot++;
+    nubus->slot_available_mask &= ~BIT(nd->slot);
 
     /* Super */
     slot_offset = nd->slot * NUBUS_SUPER_SLOT_SIZE;
@@ -191,12 +204,18 @@ static void nubus_device_realize(DeviceState *dev, Error **errp)
     nubus_register_format_block(nd);
 }
 
+static Property nubus_device_properties[] = {
+    DEFINE_PROP_INT32("slot", NubusDevice, slot, -1),
+    DEFINE_PROP_END_OF_LIST()
+};
+
 static void nubus_device_class_init(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
 
     dc->realize = nubus_device_realize;
     dc->bus_type = TYPE_NUBUS_BUS;
+    device_class_set_props(dc, nubus_device_properties);
 }
 
 static const TypeInfo nubus_device_type_info = {
