diff --git a/src/soc/amd/common/block/iommu/iommu.c b/src/soc/amd/common/block/iommu/iommu.c
index b6e4ac2..8628096 100644
--- a/src/soc/amd/common/block/iommu/iommu.c
+++ b/src/soc/amd/common/block/iommu/iommu.c
@@ -14,7 +14,7 @@
 
 	/* Add an extra subtractive resource for both memory and I/O. */
 	res = new_resource(dev, 0x44);
-	res->size = 512 * 1024;
+	res->size = 512 * KiB;
 	res->align = log2(res->size);
 	res->gran = log2(res->size);
 	res->limit = 0xffffffff;	/* 4G */