diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 1ced8a0f7a52..cba12f34ff77 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1971,7 +1971,7 @@ static int extend_iommu_mapping(struct dma_iommu_mapping *mapping)
 {
 	int next_bitmap;
 
-	if (mapping->nr_bitmaps > mapping->extensions)
+	if (mapping->nr_bitmaps >= mapping->extensions)
 		return -EINVAL;
 
 	next_bitmap = mapping->nr_bitmaps;