diff --git a/arch/openrisc/include/asm/io.h b/arch/openrisc/include/asm/io.h
index c298061c70a7..8aa3e78181e9 100644
--- a/arch/openrisc/include/asm/io.h
+++ b/arch/openrisc/include/asm/io.h
@@ -31,7 +31,7 @@
 void __iomem *ioremap(phys_addr_t offset, unsigned long size);
 
 #define iounmap iounmap
-extern void iounmap(void __iomem *addr);
+extern void iounmap(volatile void __iomem *addr);
 
 #include <asm-generic/io.h>
 
diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c
index daae13a76743..8ec0dafecf25 100644
--- a/arch/openrisc/mm/ioremap.c
+++ b/arch/openrisc/mm/ioremap.c
@@ -77,7 +77,7 @@ void __iomem *__ref ioremap(phys_addr_t addr, unsigned long size)
 }
 EXPORT_SYMBOL(ioremap);
 
-void iounmap(void __iomem *addr)
+void iounmap(volatile void __iomem *addr)
 {
 	/* If the page is from the fixmap pool then we just clear out
 	 * the fixmap mapping.