diff --git a/src/arch/i386/interface/pcbios/pcibios.c b/src/arch/i386/interface/pcbios/pcibios.c
index 9f69fe6e..511ec623 100644
--- a/src/arch/i386/interface/pcbios/pcibios.c
+++ b/src/arch/i386/interface/pcbios/pcibios.c
@@ -29,11 +29,11 @@ FILE_LICENCE ( GPL2_OR_LATER );
  */
 
 /**
- * Determine maximum PCI bus number within system
+ * Determine number of PCI buses within system
  *
- * @ret max_bus		Maximum bus number
+ * @ret num_bus		Number of buses
  */
-static int pcibios_max_bus ( void ) {
+static int pcibios_num_bus ( void ) {
 	int discard_a, discard_D;
 	uint8_t max_bus;
 
@@ -48,7 +48,7 @@ static int pcibios_max_bus ( void ) {
 				 "D" ( 0 )
 			       : "ebx", "edx" );
 
-	return max_bus;
+	return ( max_bus + 1 );
 }
 
 /**
@@ -105,7 +105,7 @@ int pcibios_write ( struct pci_device *pci, uint32_t command, uint32_t value ){
 	return ( ( status >> 8 ) & 0xff );
 }
 
-PROVIDE_PCIAPI ( pcbios, pci_max_bus, pcibios_max_bus );
+PROVIDE_PCIAPI ( pcbios, pci_num_bus, pcibios_num_bus );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_read_config_byte );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_read_config_word );
 PROVIDE_PCIAPI_INLINE ( pcbios, pci_read_config_dword );
diff --git a/src/arch/x86/core/pcidirect.c b/src/arch/x86/core/pcidirect.c
index ae74b7f1..a07f7d4b 100644
--- a/src/arch/x86/core/pcidirect.c
+++ b/src/arch/x86/core/pcidirect.c
@@ -38,7 +38,7 @@ void pcidirect_prepare ( struct pci_device *pci, int where ) {
 	       PCIDIRECT_CONFIG_ADDRESS );
 }
 
-PROVIDE_PCIAPI_INLINE ( direct, pci_max_bus );
+PROVIDE_PCIAPI_INLINE ( direct, pci_num_bus );
 PROVIDE_PCIAPI_INLINE ( direct, pci_read_config_byte );
 PROVIDE_PCIAPI_INLINE ( direct, pci_read_config_word );
 PROVIDE_PCIAPI_INLINE ( direct, pci_read_config_dword );
diff --git a/src/arch/x86/include/ipxe/pcidirect.h b/src/arch/x86/include/ipxe/pcidirect.h
index 4e933c43..7fa7c4fa 100644
--- a/src/arch/x86/include/ipxe/pcidirect.h
+++ b/src/arch/x86/include/ipxe/pcidirect.h
@@ -26,14 +26,14 @@ struct pci_device;
 extern void pcidirect_prepare ( struct pci_device *pci, int where );
 
 /**
- * Determine maximum PCI bus number within system
+ * Determine number of PCI buses within system
  *
- * @ret max_bus		Maximum bus number
+ * @ret num_bus		Number of buses
  */
 static inline __always_inline int
-PCIAPI_INLINE ( direct, pci_max_bus ) ( void ) {
+PCIAPI_INLINE ( direct, pci_num_bus ) ( void ) {
 	/* No way to work this out via Type 1 accesses */
-	return 0xff;
+	return 0x100;
 }
 
 /**
diff --git a/src/drivers/bus/pci.c b/src/drivers/bus/pci.c
index e92f11b2..a30fcc72 100644
--- a/src/drivers/bus/pci.c
+++ b/src/drivers/bus/pci.c
@@ -234,7 +234,7 @@ static int pcibus_probe ( struct root_device *rootdev ) {
 	uint32_t tmp;
 	int rc;
 
-	num_bus = ( pci_max_bus() + 1 );
+	num_bus = pci_num_bus();
 	for ( busdevfn = 0 ; busdevfn < PCI_BUSDEVFN ( num_bus, 0, 0 ) ;
 	      busdevfn++ ) {
 
diff --git a/src/include/ipxe/efi/efi_pci.h b/src/include/ipxe/efi/efi_pci.h
index b280d801..e06473d3 100644
--- a/src/include/ipxe/efi/efi_pci.h
+++ b/src/include/ipxe/efi/efi_pci.h
@@ -33,14 +33,14 @@ extern int efipci_write ( struct pci_device *pci, unsigned long location,
 			  unsigned long value );
 
 /**
- * Determine maximum PCI bus number within system
+ * Determine number of PCI buses within system
  *
- * @ret max_bus		Maximum bus number
+ * @ret num_bus		Number of buses
  */
 static inline __always_inline int
-PCIAPI_INLINE ( efi, pci_max_bus ) ( void ) {
+PCIAPI_INLINE ( efi, pci_num_bus ) ( void ) {
 	/* No way to work this out via EFI */
-	return 0xff;
+	return 0x100;
 }
 
 /**
diff --git a/src/include/ipxe/pci_io.h b/src/include/ipxe/pci_io.h
index 11880907..dab5b780 100644
--- a/src/include/ipxe/pci_io.h
+++ b/src/include/ipxe/pci_io.h
@@ -49,11 +49,11 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <bits/pci_io.h>
 
 /**
- * Determine maximum PCI bus number within system
+ * Determine number of PCI buses within system
  *
- * @ret max_bus		Maximum bus number
+ * @ret num_bus		Number of buses
  */
-int pci_max_bus ( void );
+int pci_num_bus ( void );
 
 /**
  * Read byte from PCI configuration space
diff --git a/src/interface/efi/efi_pci.c b/src/interface/efi/efi_pci.c
index c240d4cb..eb334b68 100644
--- a/src/interface/efi/efi_pci.c
+++ b/src/interface/efi/efi_pci.c
@@ -73,7 +73,7 @@ int efipci_write ( struct pci_device *pci, unsigned long location,
 	return 0;
 }
 
-PROVIDE_PCIAPI_INLINE ( efi, pci_max_bus );
+PROVIDE_PCIAPI_INLINE ( efi, pci_num_bus );
 PROVIDE_PCIAPI_INLINE ( efi, pci_read_config_byte );
 PROVIDE_PCIAPI_INLINE ( efi, pci_read_config_word );
 PROVIDE_PCIAPI_INLINE ( efi, pci_read_config_dword );