diff --git a/Cargo.toml b/Cargo.toml
index b53393a..512538f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,8 +1,8 @@
 [package]
 name = "tinymt"
-version = "1.0.6"
+version = "1.0.7"
 authors = ["Torao Takami <koiroha@gmail.com>"]
-edition = "2018"
+edition = "2021"
 repository = "https://github.com/torao/tinymt"
 keywords = ["prng", "mersennetwister", "mt", "tinymt", "random"]
 license = "MIT"
diff --git a/README.md b/README.md
index 0ee7ea2..f2b2435 100644
--- a/README.md
+++ b/README.md
@@ -75,6 +75,7 @@ $ cargo +nightly fmt       # or fmt -- --check
 
 ## History
 
+* 2022-05-19 (v1.0.7) Migrate the project to 2021 edition.
 * 2021-06-12 (v1.0.6) Upgrade `rand` to 0.8.
 
 ## Licenses
diff --git a/src/lib.rs b/src/lib.rs
index f5900bc..2a9f06b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,7 @@ use rand::{Error, RngCore, SeedableRng};
 pub mod tinymt32;
 pub mod tinymt64;
 
+#[derive(Default)]
 pub struct TinyMT64Seed(pub [u8; 8]);
 
 impl From<u64> for TinyMT64Seed {
@@ -19,12 +20,6 @@ impl From<TinyMT64Seed> for u64 {
   }
 }
 
-impl Default for TinyMT64Seed {
-  fn default() -> TinyMT64Seed {
-    TinyMT64Seed([0; 8])
-  }
-}
-
 impl AsMut<[u8]> for TinyMT64Seed {
   fn as_mut(&mut self) -> &mut [u8] {
     &mut self.0
@@ -84,6 +79,7 @@ impl RngCore for TinyMT64 {
   }
 }
 
+#[derive(Default)]
 pub struct TinyMT32Seed(pub [u8; 4]);
 
 impl From<u32> for TinyMT32Seed {
@@ -98,12 +94,6 @@ impl From<TinyMT32Seed> for u32 {
   }
 }
 
-impl Default for TinyMT32Seed {
-  fn default() -> TinyMT32Seed {
-    TinyMT32Seed([0; 4])
-  }
-}
-
 impl AsMut<[u8]> for TinyMT32Seed {
   fn as_mut(&mut self) -> &mut [u8] {
     &mut self.0