diff --git a/src/device/pci_bridge.c b/src/device/pci_bridge.c
index 8893acf69..bf49baf14 100644
--- a/src/device/pci_bridge.c
+++ b/src/device/pci_bridge.c
@@ -87,6 +87,14 @@ pci_bridge_set_ctl(void *priv, uint8_t ctl)
     dev->ctl = ctl;
 }
 
+uint8_t
+pci_bridge_get_bus_index(void *priv)
+{
+    pci_bridge_t *dev = (pci_bridge_t *) priv;
+
+    return dev->bus_index;
+}
+
 static void
 pci_bridge_write(int func, int addr, uint8_t val, void *priv)
 {
@@ -513,11 +521,9 @@ static void *
 pci_bridge_init(const device_t *info)
 {
     uint8_t interrupts[4];
-    uint8_t interrupt_count;
     uint8_t interrupt_mask;
+    uint8_t add_type;
     uint8_t slot_count;
-    uint8_t dell_slots[3]         = { 0x09, 0x0a, 0x0b };
-    uint8_t dell_interrupts[3][4] = { { 1, 2, 3, 4 }, { 4, 2, 1, 3 }, { 1, 3, 4, 2 } };
 
     pci_bridge_t *dev = (pci_bridge_t *) calloc(1, sizeof(pci_bridge_t));
 
@@ -527,40 +533,35 @@ pci_bridge_init(const device_t *info)
 
     pci_bridge_reset(dev);
 
-    if (info->local == PCI_BRIDGE_DEC_21152)
-        pci_add_card(PCI_ADD_BRIDGE, pci_bridge_read, pci_bridge_write, dev, &dev->slot);
-    else
-        pci_add_bridge(AGP_BRIDGE(dev->local), pci_bridge_read, pci_bridge_write, dev, &dev->slot);
-
-    interrupt_count = sizeof(interrupts);
-    interrupt_mask  = interrupt_count - 1;
+    interrupt_mask = sizeof(interrupts) - 1;
     if (dev->slot < 32) {
-        for (uint8_t i = 0; i < interrupt_count; i++)
+        for (uint8_t i = 0; i <= interrupt_mask; i++)
             interrupts[i] = pci_get_int(dev->slot, PCI_INTA + i);
     }
     pci_bridge_log("PCI Bridge %d: upstream bus %02X slot %02X interrupts %02X %02X %02X %02X\n",
                    dev->bus_index, (dev->slot >> 5) & 0xff, dev->slot & 31, interrupts[0],
                    interrupts[1], interrupts[2], interrupts[3]);
 
-    if (info->local == PCI_BRIDGE_DEC_21150)
+    if (info->local == PCI_BRIDGE_DEC_21150) {
         slot_count = 9; /* 9 bus masters */
-    else if (info->local == PCI_BRIDGE_DEC_21152)
-        slot_count = 3; /* 3 bus masters */
-    else
+        add_type   = PCI_ADD_NORMAL;
+    } else if (info->local == PCI_BRIDGE_DEC_21152) {
+        slot_count = 0; /* 4 bus masters, but slots are added by the Dell machines */
+        add_type   = PCI_ADD_BRIDGE;
+    } else {
         slot_count = 1; /* AGP bridges always have 1 slot */
+        add_type   = PCI_ADD_AGPBRIDGE;
+    }
+
+    pci_add_bridge(add_type, pci_bridge_read, pci_bridge_write, dev, &dev->slot);
 
     for (uint8_t i = 0; i < slot_count; i++) {
-        uint8_t slot = i;
-        if (info->local == PCI_BRIDGE_DEC_21152) {
-            slot = dell_slots[i];
-            memcpy(interrupts, dell_interrupts[i], 4);
-        }
         /* Interrupts for bridge slots are assigned in round-robin: ABCD, BCDA, CDAB and so on. */
         pci_bridge_log("PCI Bridge %d: downstream slot %02X interrupts %02X %02X %02X %02X\n",
-                       dev->bus_index, slot, interrupts[i & interrupt_mask],
+                       dev->bus_index, i, interrupts[i & interrupt_mask],
                        interrupts[(i + 1) & interrupt_mask], interrupts[(i + 2) & interrupt_mask],
                        interrupts[(i + 3) & interrupt_mask]);
-        pci_register_bus_slot(dev->bus_index, slot, AGP_BRIDGE(dev->local) ? PCI_CARD_AGP : PCI_CARD_NORMAL,
+        pci_register_bus_slot(dev->bus_index, i, AGP_BRIDGE(dev->local) ? PCI_CARD_AGP : PCI_CARD_NORMAL,
                               interrupts[i & interrupt_mask],
                               interrupts[(i + 1) & interrupt_mask],
                               interrupts[(i + 2) & interrupt_mask],
diff --git a/src/include/86box/machine.h b/src/include/86box/machine.h
index 4129cead7..3231acd80 100644
--- a/src/include/86box/machine.h
+++ b/src/include/86box/machine.h
@@ -722,6 +722,8 @@ extern int machine_at_vectra54_init(const machine_t *);
 extern int machine_at_5sbm2_init(const machine_t *);
 
 /* m_at_socket7.c */
+extern void machine_at_optiplex_21152_init(void);
+
 extern int machine_at_acerv35n_init(const machine_t *);
 extern int machine_at_p55t2p4_init(const machine_t *);
 extern int machine_at_m7shi_init(const machine_t *);
diff --git a/src/include/86box/pci.h b/src/include/86box/pci.h
index 462b4f821..8887f89f4 100644
--- a/src/include/86box/pci.h
+++ b/src/include/86box/pci.h
@@ -283,6 +283,7 @@ extern void        pci_init(int flags);
 
 /* PCI bridge stuff. */
 extern void        pci_bridge_set_ctl(void *priv, uint8_t ctl);
+extern uint8_t     pci_bridge_get_bus_index(void *priv);
 
 #ifdef EMU_DEVICE_H
 extern const device_t dec21150_device;
diff --git a/src/machine/m_at_slot1.c b/src/machine/m_at_slot1.c
index 280462858..2ac805bee 100644
--- a/src/machine/m_at_slot1.c
+++ b/src/machine/m_at_slot1.c
@@ -170,14 +170,14 @@ machine_at_optiplexgxa_init(const machine_t *model)
     pci_register_slot(0x11, PCI_CARD_NETWORK,     4, 0, 0, 0);
     pci_register_slot(0x0E, PCI_CARD_NORMAL,      3, 4, 2, 1);
     pci_register_slot(0x0D, PCI_CARD_NORMAL,      2, 1, 3, 4);
-    pci_register_slot(0x0F, PCI_CARD_BRIDGE,      1, 2, 3, 4);
+    pci_register_slot(0x0F, PCI_CARD_BRIDGE,      0, 0, 0, 0);
 
     if (sound_card_current[0] == SOUND_INTERNAL)
         device_add(machine_get_snd_device(machine));
 
     device_add(&i440lx_device);
     device_add(&piix4_device);
-    device_add(&dec21152_device);
+    machine_at_optiplex_21152_init();
     device_add_params(&pc87307_device, (void *) (PCX730X_PHOENIX_42 | PCX7307_PC87307));
     device_add(&intel_flash_bxt_device);
     spd_register(SPD_TYPE_SDRAM, 0x7, 256);
diff --git a/src/machine/m_at_socket7.c b/src/machine/m_at_socket7.c
index dbc59ef17..46c7b7623 100644
--- a/src/machine/m_at_socket7.c
+++ b/src/machine/m_at_socket7.c
@@ -46,6 +46,15 @@
 #include <86box/network.h>
 #include <86box/pci.h>
 
+void
+machine_at_optiplex_21152_init(void)
+{
+    uint8_t bus_index = pci_bridge_get_bus_index(device_add(&dec21152_device));
+    pci_register_bus_slot(bus_index, 0x09, PCI_CARD_NORMAL, 1, 2, 3, 4);
+    pci_register_bus_slot(bus_index, 0x0a, PCI_CARD_NORMAL, 4, 2, 1, 3);
+    pci_register_bus_slot(bus_index, 0x0b, PCI_CARD_NORMAL, 1, 3, 4, 2);
+}
+
 int
 machine_at_acerv35n_init(const machine_t *model)
 {
@@ -989,7 +998,7 @@ machine_at_optiplexgn_init(const machine_t *model)
     pci_register_slot(0x10, PCI_CARD_VIDEO,       4, 0, 0, 0); /* Trio64V2/GX, temporarily Trio64V2/DX is given */
     pci_register_slot(0x11, PCI_CARD_NETWORK,     4, 0, 0, 0); /* 3C905, not yet emulated */
     pci_register_slot(0x07, PCI_CARD_SOUTHBRIDGE, 0, 0, 0, 4);
-    pci_register_slot(0x0F, PCI_CARD_BRIDGE,      1, 2, 3, 4);
+    pci_register_slot(0x0F, PCI_CARD_BRIDGE,      0, 0, 0, 0);
 
     if (gfxcard[0] == VID_INTERNAL)
         device_add(machine_get_vid_device(machine));
@@ -999,7 +1008,7 @@ machine_at_optiplexgn_init(const machine_t *model)
 
     device_add(&i430tx_device);
     device_add(&piix4_device);
-    device_add(&dec21152_device);
+    machine_at_optiplex_21152_init();
     device_add_params(&pc87307_device, (void *) (PCX730X_PHOENIX_42 | PCX7307_PC87307));
     device_add(&intel_flash_bxt_device);
     spd_register(SPD_TYPE_SDRAM, 0x3, 128);
diff --git a/src/pci.c b/src/pci.c
index c3020ca73..94ab9d5f2 100644
--- a/src/pci.c
+++ b/src/pci.c
@@ -855,10 +855,10 @@ pci_register_card(int pci_card)
 
 /* Add an instance of the PCI bridge. */
 void
-pci_add_bridge(uint8_t agp, uint8_t (*read)(int func, int addr, void *priv), void (*write)(int func, int addr, uint8_t val, void *priv), void *priv, uint8_t *slot)
+pci_add_bridge(uint8_t add_type, uint8_t (*read)(int func, int addr, void *priv), void (*write)(int func, int addr, uint8_t val, void *priv), void *priv, uint8_t *slot)
 {
     pci_card_t *card;
-    uint8_t bridge_slot = agp ? pci_find_slot(PCI_ADD_AGPBRIDGE, 0xff) : last_normal_pci_card_id;
+    uint8_t bridge_slot = (add_type == PCI_ADD_NORMAL) ? last_normal_pci_card_id : pci_find_slot(add_type, 0xff);
 
     if (bridge_slot != PCI_CARD_INVALID) {
         card = &pci_cards[bridge_slot];