diff --git a/arch/x86/include/asm/dma.h b/arch/x86/include/asm/dma.h
index 0bdb0c5..fe884e1 100644
--- a/arch/x86/include/asm/dma.h
+++ b/arch/x86/include/asm/dma.h
@@ -70,7 +70,7 @@
 #define MAX_DMA_CHANNELS	8
 
 /* 16MB ISA DMA zone */
-#define MAX_DMA_PFN   ((16 * 1024 * 1024) >> PAGE_SHIFT)
+#define MAX_DMA_PFN   ((16UL * 1024 * 1024) >> PAGE_SHIFT)
 
 /* 4GB broken PCI/AGP hardware bus master zone */
 #define MAX_DMA32_PFN ((4UL * 1024 * 1024 * 1024) >> PAGE_SHIFT)