diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 6499bda8f0b809c967e9f895ddd2877994f724d4..465a567678d9663d28790b08222485cea9d4f10b 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -93,7 +93,7 @@ static unsigned int io_tlb_index;
  * Max segment that we can provide which (if pages are contingous) will
  * not be bounced (unless SWIOTLB_FORCE is set).
  */
-unsigned int max_segment;
+static unsigned int max_segment;
 
 /*
  * We need to save away the original address corresponding to a mapped entry