diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index fc91205ff46c..5bf9443cfbaa 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -473,7 +473,7 @@ void pci_ioremap_set_mem_type(int mem_type)
 
 int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr)
 {
-	BUG_ON(offset + SZ_64K > IO_SPACE_LIMIT);
+	BUG_ON(offset + SZ_64K - 1 > IO_SPACE_LIMIT);
 
 	return ioremap_page_range(PCI_IO_VIRT_BASE + offset,
 				  PCI_IO_VIRT_BASE + offset + SZ_64K,