diff --git a/Cargo.toml b/Cargo.toml
index 1a082ff..5d3cd34 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,8 +26,8 @@ license = "Apache-2.0"
 maintenance = { status = "actively-developed" }
 
 [dependencies]
-num = "0.2"
-derive_builder = "0.7"
+num = "0.4"
+derive_builder = "0.12"
 serde = { version = "1.0.152", features = ["derive"], optional=true}
 
 [features]
diff --git a/src/area.rs b/src/area.rs
index a93e1a5..57b55f8 100644
--- a/src/area.rs
+++ b/src/area.rs
@@ -14,6 +14,7 @@
 
 //! A rectangular region in the tree.
 
+use derive_builder::Builder;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 use {
diff --git a/src/lib.rs b/src/lib.rs
index 7073e23..02a278b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -113,10 +113,6 @@
 // For extra-pedantic documentation tests.
 #![doc(test(attr(deny(warnings))))]
 
-#[macro_use]
-extern crate derive_builder;
-extern crate num;
-
 pub mod area;
 pub mod entry;
 pub mod iter;
@@ -171,7 +167,7 @@ use {
 /// operational region, the strict behavior is for the operation to apply only to those regions
 /// which are _totally contained by_ the operational region.
 ///
-/// [`derive_builder`]: https://docs.rs/derive_builder/0.7.0/derive_builder/
+/// [`derive_builder`]: https://docs.rs/derive_builder/0.12.0/derive_builder/
 /// [`.query()`]: #method.query
 /// [`.modify()`]: #method.modify
 /// [`.delete()`]: #method.delete