diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 019e02707cd5e3c893b3b6602a1847260b3ba401..3ef0f42984f2b1ec716509203988f9ebb70533cb 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1023,7 +1023,7 @@ static int __iommu_queue_command_sync(struct amd_iommu *iommu,
 	next_tail = (tail + sizeof(*cmd)) % CMD_BUFFER_SIZE;
 	left      = (head - next_tail) % CMD_BUFFER_SIZE;
 
-	if (left <= 2) {
+	if (left <= 0x20) {
 		struct iommu_cmd sync_cmd;
 		int ret;