diff --git a/src/config.sh b/src/config.sh
index 866153a..f4bfe3f 100644
--- a/src/config.sh
+++ b/src/config.sh
@@ -41,9 +41,12 @@ configureMachine() {
 
 configureVirtioDevices() {
 
-  DEV_OPTS="-device virtio-balloon-pci,id=balloon0,bus=pcie.0,addr=0x4"
+  local bus
+  bus=$(getPciBus)
+
+  DEV_OPTS="-device virtio-balloon-pci,id=balloon0,bus=$bus,addr=0x4"
   DEV_OPTS+=" -object rng-random,id=objrng0,filename=/dev/urandom"
-  DEV_OPTS+=" -device virtio-rng-pci,rng=objrng0,id=rng0,bus=pcie.0,addr=0x1c"
+  DEV_OPTS+=" -device virtio-rng-pci,rng=objrng0,id=rng0,bus=$bus,addr=0x1c"
 
   return 0
 }
diff --git a/src/disk.sh b/src/disk.sh
index 20d5a76..16849b6 100644
--- a/src/disk.sh
+++ b/src/disk.sh
@@ -518,11 +518,9 @@ createDevice () {
   local diskCache="$7"
   local diskSerial="$8"
   local diskSectors="$9"
-  local bus="${PCI_BUS:-pcie.0}"
 
-  # q35 uses pcie.0, while legacy pc/i440fx machines expose their devices on
-  # pci.0 unless the caller supplied an explicit bus.
-  [[ -z "${PCI_BUS:-}" && ( "${MACHINE,,}" == pc || "${MACHINE,,}" == pc-i440fx* ) ]] && bus="pci.0"
+  local bus
+  bus=$(getPciBus)
 
   local options=""
   [ -n "$DISK_OPTIONS" ] && options=",${DISK_OPTIONS#,}"
diff --git a/src/serial.sh b/src/serial.sh
index 37e26f3..0a66e58 100644
--- a/src/serial.sh
+++ b/src/serial.sh
@@ -111,6 +111,9 @@ waitForSocket() {
 
 configureSerialPorts() {
 
+  local bus
+  bus=$(getPciBus)
+
   # Managed interactive mode separates the console and QEMU monitor into
   # reconnecting sockets; other runs keep the simple combined stdio monitor.
   if enabled "${SHUTDOWN:-Y}" && interactive; then
@@ -130,7 +133,7 @@ configureSerialPorts() {
   fi
 
   SERIAL_OPTS+=" \
-        -device virtio-serial-pci,id=virtio-serial0,bus=pcie.0,addr=0x3 \
+        -device virtio-serial-pci,id=virtio-serial0,bus=$bus,addr=0x3 \
         -chardev socket,id=charchannel0,path=$HOST_AGENT_SOCKET,reconnect-ms=1000 \
         -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=vchannel"
 
diff --git a/src/utils.sh b/src/utils.sh
index d0e3d90..25f0ea4 100644
--- a/src/utils.sh
+++ b/src/utils.sh
@@ -49,6 +49,23 @@ isAmdCpu() {
   [[ "$vendor" == "AuthenticAMD" ]]
 }
 
+getPciBus() {
+
+  local machine="${1:-${MACHINE:-q35}}"
+
+  if [ -n "${PCI_BUS:-}" ]; then
+    echo "$PCI_BUS"
+    return 0
+  fi
+
+  case "${machine,,}" in
+    pc|pc-i440fx*) echo "pci.0" ;;
+    *)             echo "pcie.0" ;;
+  esac
+
+  return 0
+}
+
 interactive() {
 
   # A TTY on stdin is insufficient when /dev/tty is unavailable; require both