diff --git a/Cargo.toml b/Cargo.toml
index a509f49..9a5ac5d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,7 +16,7 @@ name = "chrono"
 
 [dependencies]
 time = "0.1"
-num = "0.1"
+num = { version = "0.1", default-features = false }
 rustc-serialize = { version = "0.3", optional = true }
 serde = { version = "^0.6.0", optional = true }