diff --git a/Cargo.toml b/Cargo.toml
index 363c1fe..ede3c48 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,10 @@ name = "chrono"
 version = "0.1.0"
 authors = ["Kang Seonghoon <public+rust@mearie.org>"]
 
+[dependencies.num]
+
+git = "https://github.com/rust-lang/num"
+
 [lib]
 
 name = "chrono"