diff --git a/drivers/serial/m32r_sio.h b/drivers/serial/m32r_sio.h
index 07d0dd80aa3d..7c3ec24f7e50 100644
--- a/drivers/serial/m32r_sio.h
+++ b/drivers/serial/m32r_sio.h
@@ -37,7 +37,7 @@ struct old_serial_port {
 	unsigned int irq;
 	unsigned int flags;
 	unsigned char io_type;
-	unsigned char *iomem_base;
+	unsigned char __iomem *iomem_base;
 	unsigned short iomem_reg_shift;
 };