diff --git a/src/add-ons/kernel/file_systems/exfat/DataStream.cpp b/src/add-ons/kernel/file_systems/exfat/DataStream.cpp
index 5a9647e7c8..f1123c1954 100644
--- a/src/add-ons/kernel/file_systems/exfat/DataStream.cpp
+++ b/src/add-ons/kernel/file_systems/exfat/DataStream.cpp
@@ -52,7 +52,8 @@ DataStream::FindBlock(off_t pos, off_t& physical, off_t *_length)
 	for (uint32 i = 0; i < clusterIndex; i++)
 		cluster = fInode->NextCluster(cluster);
 	fsblock_t block;
-	fVolume->ClusterToBlock(cluster, block);
+	if (fVolume->ClusterToBlock(cluster, block) != B_OK)
+		return B_BAD_DATA;
 	physical = block * kBlockSize + offset;
 	for (uint32 i = 0; i < 64; i++) {
 		cluster_t extentEnd = fInode->NextCluster(cluster);
diff --git a/src/add-ons/kernel/file_systems/exfat/DirectoryIterator.cpp b/src/add-ons/kernel/file_systems/exfat/DirectoryIterator.cpp
index 278af03b1e..24e81d1c53 100644
--- a/src/add-ons/kernel/file_systems/exfat/DirectoryIterator.cpp
+++ b/src/add-ons/kernel/file_systems/exfat/DirectoryIterator.cpp
@@ -275,7 +275,8 @@ DirectoryIterator::_NextEntry()
 {
 	if (fCurrent == NULL) {
 		fsblock_t block;
-		fInode->GetVolume()->ClusterToBlock(fCluster, block);
+		if (fInode->GetVolume()->ClusterToBlock(fCluster, block) != B_OK)
+			return B_BAD_DATA;
 		block += (fOffset / fInode->GetVolume()->EntriesPerBlock())
 			% (1 << fInode->GetVolume()->SuperBlock().BlocksPerClusterShift());
 		TRACE("DirectoryIterator::_NextEntry() init to block %" B_PRIu64 "\n",
@@ -289,7 +290,8 @@ DirectoryIterator::_NextEntry()
 			if (fCluster == EXFAT_CLUSTER_END)
 				return B_ENTRY_NOT_FOUND;
 
-			fInode->GetVolume()->ClusterToBlock(fCluster, block);
+			if (fInode->GetVolume()->ClusterToBlock(fCluster, block) != B_OK)
+				return B_BAD_DATA;
 		} else
 			block = fBlock.BlockNumber() + 1;
 
diff --git a/src/add-ons/kernel/file_systems/exfat/Volume.cpp b/src/add-ons/kernel/file_systems/exfat/Volume.cpp
index aa9dbbe5e3..b6f7b1a7f3 100644
--- a/src/add-ons/kernel/file_systems/exfat/Volume.cpp
+++ b/src/add-ons/kernel/file_systems/exfat/Volume.cpp
@@ -416,8 +416,10 @@ Volume::LoadSuperBlock()
 status_t
 Volume::ClusterToBlock(cluster_t cluster, fsblock_t &block)
 {
-	if (cluster < EXFAT_FIRST_DATA_CLUSTER)
+	if ((cluster - EXFAT_FIRST_DATA_CLUSTER) >= SuperBlock().ClusterCount()
+		|| cluster < EXFAT_FIRST_DATA_CLUSTER) {
 		return B_BAD_VALUE;
+	}
 	block = ((fsblock_t)(cluster - EXFAT_FIRST_DATA_CLUSTER)
 		<< SuperBlock().BlocksPerClusterShift())
 		+ SuperBlock().FirstDataBlock();
diff --git a/src/add-ons/kernel/file_systems/exfat/exfat.h b/src/add-ons/kernel/file_systems/exfat/exfat.h
index b33888eb46..09a7d326ea 100644
--- a/src/add-ons/kernel/file_systems/exfat/exfat.h
+++ b/src/add-ons/kernel/file_systems/exfat/exfat.h
@@ -170,7 +170,7 @@ struct exfat_entry {
 			void SetFlag(uint8 newFlag)
 				{ flag = newFlag; }
 			uint64 Size() const
-				{ return B_LENDIAN_TO_HOST_INT64(size1); }
+				{ return B_LENDIAN_TO_HOST_INT64(size2); }
 		} _PACKED file_info;
 		struct {
 			uint8 flags;