diff --git a/plat/imx/imx7/warp7/include/platform_def.h b/plat/imx/imx7/warp7/include/platform_def.h
index d0148f4..4ee6fd3 100644
--- a/plat/imx/imx7/warp7/include/platform_def.h
+++ b/plat/imx/imx7/warp7/include/platform_def.h
@@ -169,7 +169,7 @@
 #define MAX_XLAT_TABLES			6
 #define MAX_IO_DEVICES			2
 #define MAX_IO_HANDLES			3
-#define MAX_IO_BLOCK_DEVICES		1
+#define MAX_IO_BLOCK_DEVICES		1U
 
 /* UART defines */
 #if PLAT_WARP7_UART == 1