diff --git a/arch/microblaze/include/asm/io.h b/arch/microblaze/include/asm/io.h
index 39b6315db82e..c7968139486f 100644
--- a/arch/microblaze/include/asm/io.h
+++ b/arch/microblaze/include/asm/io.h
@@ -36,7 +36,7 @@ extern resource_size_t isa_mem_base;
 #ifdef CONFIG_MMU
 #define page_to_bus(page)	(page_to_phys(page))
 
-extern void iounmap(void __iomem *addr);
+extern void iounmap(volatile void __iomem *addr);
 
 extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
 #define ioremap_nocache(addr, size)		ioremap((addr), (size))
diff --git a/arch/microblaze/mm/pgtable.c b/arch/microblaze/mm/pgtable.c
index 4c0599239915..7f525962cdfa 100644
--- a/arch/microblaze/mm/pgtable.c
+++ b/arch/microblaze/mm/pgtable.c
@@ -127,7 +127,7 @@ void __iomem *ioremap(phys_addr_t addr, unsigned long size)
 }
 EXPORT_SYMBOL(ioremap);
 
-void iounmap(void __iomem *addr)
+void iounmap(volatile void __iomem *addr)
 {
 	if ((__force void *)addr > high_memory &&
 					(unsigned long) addr < ioremap_bot)