diff --git a/block/bochs.c b/block/bochs.c
index ef8e381ba00ad0c8533704203521e947e1e5c5a7..e923eedf3e0223321a424f62c62fb446c5cfc520 100644
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -67,13 +67,13 @@ struct bochs_header {
 typedef struct BDRVBochsState {
     CoMutex lock;
     uint32_t *catalog_bitmap;
-    int catalog_size;
+    uint32_t catalog_size;
 
-    int data_offset;
+    uint32_t data_offset;
 
-    int bitmap_blocks;
-    int extent_blocks;
-    int extent_size;
+    uint32_t bitmap_blocks;
+    uint32_t extent_blocks;
+    uint32_t extent_size;
 } BDRVBochsState;
 
 static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
@@ -97,7 +97,7 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
                       Error **errp)
 {
     BDRVBochsState *s = bs->opaque;
-    int i;
+    uint32_t i;
     struct bochs_header bochs;
     int ret;
 
@@ -153,8 +153,8 @@ fail:
 static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
 {
     BDRVBochsState *s = bs->opaque;
-    int64_t offset = sector_num * 512;
-    int64_t extent_index, extent_offset, bitmap_offset;
+    uint64_t offset = sector_num * 512;
+    uint64_t extent_index, extent_offset, bitmap_offset;
     char bitmap_entry;
 
     // seek to sector
diff --git a/tests/qemu-iotests/078 b/tests/qemu-iotests/078
index f55f46d92b88766cd2d81e53563ccf4ccd7b9fe9..73b573a624d7b9a0206024493eda725037bc2132 100755
--- a/tests/qemu-iotests/078
+++ b/tests/qemu-iotests/078
@@ -42,11 +42,19 @@ _supported_fmt bochs
 _supported_proto generic
 _supported_os Linux
 
+catalog_size_offset=$((0x48))
+
 echo
 echo "== Read from a valid image =="
 _use_sample_img empty.bochs.bz2
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "== Negative catalog size =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$catalog_size_offset" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/078.out b/tests/qemu-iotests/078.out
index 25d37c5dcd0d0f3da3e6e8eeea6797aa38380754..ef8c42de9c1a805d76b6e37012c6439dacdb32d9 100644
--- a/tests/qemu-iotests/078.out
+++ b/tests/qemu-iotests/078.out
@@ -3,4 +3,8 @@ QA output created by 078
 == Read from a valid image ==
 read 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== Negative catalog size ==
+qemu-io: can't open device TEST_DIR/empty.bochs: Could not open 'TEST_DIR/empty.bochs': Interrupted system call
+no file open, try 'help open'
 *** done