diff --git a/Cargo.toml b/Cargo.toml
index c8c47835..10a5675b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "fid-rs"
-version = "0.2.0"
+version = "0.2.1"
 authors = ["Sho Nakatani <lay.sakura@gmail.com>"]
 description = "High performance FID (Fully Indexable Dictionary) library"
 readme = "README.md"
@@ -18,7 +18,7 @@ rayon = { version = "1.5", optional = true }
 # Serde is another optional feature, which can be enabled by setting `serde` feature.
 # It is used to serialize and deserialize the FID structure.
 serde = { version = "1.0", optional = true, features = ["derive"] }
-mem_dbg = {version = "0.1.4", optional = true}
+mem_dbg = {version = "0.2.2", optional = true}
 
 [dev-dependencies]
 criterion = "0.5"