diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index e93375c710b9..dea1d36a6402 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -957,7 +957,7 @@ static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
 
 #ifndef iounmap
 #define iounmap iounmap
-static inline void iounmap(void __iomem *addr)
+static inline void iounmap(volatile void __iomem *addr)
 {
 }
 #endif