diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c
index 0c829edb..42096a4f 100644
--- a/lib/ext2fs/alloc.c
+++ b/lib/ext2fs/alloc.c
@@ -52,23 +52,8 @@ static void check_block_uninit(ext2_filsys fs, ext2fs_block_bitmap map,
 	else
 		old_desc_blocks = fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
 
-	for (i=0; i < fs->super->s_blocks_per_group; i++, blk++)
-		ext2fs_fast_unmark_block_bitmap2(map, blk);
+	/* uninit block bitmaps are now initialized in read_bitmaps() */
 
-	blk = ext2fs_group_first_block2(fs, group);
-	for (i=0; i < fs->super->s_blocks_per_group; i++, blk++) {
-		if ((blk == super_blk) ||
-		    (old_desc_blk && old_desc_blocks &&
-		     (blk >= old_desc_blk) &&
-		     (blk < old_desc_blk + old_desc_blocks)) ||
-		    (new_desc_blk && (blk == new_desc_blk)) ||
-		    (blk == ext2fs_block_bitmap_loc(fs, group)) ||
-		    (blk == ext2fs_inode_bitmap_loc(fs, group)) ||
-		    (blk >= ext2fs_inode_table_loc(fs, group) &&
-		     (blk < ext2fs_inode_table_loc(fs, group)
-		      + fs->inode_blocks_per_group)))
-			ext2fs_fast_mark_block_bitmap2(map, blk);
-	}
 	ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
 	ext2fs_group_desc_csum_set(fs, group);
 	ext2fs_mark_super_dirty(fs);
diff --git a/lib/ext2fs/rw_bitmaps.c b/lib/ext2fs/rw_bitmaps.c
index b7d65a9d..d24ba9a3 100644
--- a/lib/ext2fs/rw_bitmaps.c
+++ b/lib/ext2fs/rw_bitmaps.c
@@ -145,6 +145,43 @@ errout:
 	return retval;
 }
 
+static errcode_t mark_uninit_bg_group_blocks(ext2_filsys fs)
+{
+	dgrp_t			i;
+	blk64_t			blk;
+	ext2fs_block_bitmap	bmap = fs->block_map;
+
+	for (i = 0; i < fs->group_desc_count; i++) {
+		if (!ext2fs_bg_flags_test(fs, i, EXT2_BG_BLOCK_UNINIT))
+			continue;
+
+		ext2fs_reserve_super_and_bgd(fs, i, bmap);
+
+		/*
+		 * Mark the blocks used for the inode table
+		 */
+		blk = ext2fs_inode_table_loc(fs, i);
+		if (blk)
+			ext2fs_mark_block_bitmap_range2(bmap, blk,
+						fs->inode_blocks_per_group);
+
+		/*
+		 * Mark block used for the block bitmap
+		 */
+		blk = ext2fs_block_bitmap_loc(fs, i);
+		if (blk)
+			ext2fs_mark_block_bitmap2(bmap, blk);
+
+		/*
+		 * Mark block used for the inode bitmap
+		 */
+		blk = ext2fs_inode_bitmap_loc(fs, i);
+		if (blk)
+			ext2fs_mark_block_bitmap2(bmap, blk);
+	}
+	return 0;
+}
+
 static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 {
 	dgrp_t i;
@@ -292,6 +329,14 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 			ino_itr += inode_nbytes << 3;
 		}
 	}
+
+	/* Mark group blocks for any BLOCK_UNINIT groups */
+	if (do_block) {
+		retval = mark_uninit_bg_group_blocks(fs);
+		if (retval)
+			goto cleanup;
+	}
+
 success_cleanup:
 	if (inode_bitmap)
 		ext2fs_free_mem(&inode_bitmap);