diff --git a/arch/x86/kernel/pci-dma_64.c b/arch/x86/kernel/pci-dma_64.c
index b2b42bdb0a15..afaf9f12c032 100644
--- a/arch/x86/kernel/pci-dma_64.c
+++ b/arch/x86/kernel/pci-dma_64.c
@@ -11,7 +11,7 @@
 #include <asm/iommu.h>
 #include <asm/calgary.h>
 
-int iommu_merge __read_mostly = 0;
+int iommu_merge __read_mostly = 1;
 EXPORT_SYMBOL(iommu_merge);
 
 dma_addr_t bad_dma_address __read_mostly;