diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 04788940afaf..64af1c7f95c2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5134,10 +5134,10 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
 	return NULL;
 }
 
-#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
 					u64 start)
 {
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 	struct extent_buffer *eb, *exists = NULL;
 	int ret;
 
@@ -5173,8 +5173,11 @@ again:
 free_eb:
 	btrfs_release_extent_buffer(eb);
 	return exists;
-}
+#else
+	/* Stub to avoid linker error when compiled with optimizations turned off. */
+	return NULL;
 #endif
+}
 
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start)