diff --git a/Cargo.lock b/Cargo.lock
index 8c10247..95382ce 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -31,6 +31,9 @@ name = "allocator-api2"
 version = "0.2.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "683d7910e743518b0e34f1186f92494becacb047c7b6bf616c96772180fef923"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "android-tzdata"
@@ -821,6 +824,26 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "serde"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f0e2c6ed6606019b4e29e69dbaba95b11854410e5347d525002456dbbb786b6"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.219"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b0276cf7f2c73365f7157c8123c21cd9a50fbbd844757af28ca1f5925fc2a00"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "sha2"
 version = "0.10.9"
diff --git a/Cargo.toml b/Cargo.toml
index 7799118..a035054 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,10 @@ async = [
 # Enables the components using memory allocation.
 # If no `std` flag, `alloc` crate is internally used instead. This flag is mainly for `no_std` build.
 alloc = ["allocator-api2/alloc"]
+# Enables serde support for some of the provided types.
+serde = [
+    "allocator-api2/serde",
+]
 # Enables the components using `std` crate.
 std = [
     "alloc",
diff --git a/examples/shared_dict.rs b/examples/shared_dict.rs
index 5f293e9..0c02e0f 100644
--- a/examples/shared_dict.rs
+++ b/examples/shared_dict.rs
@@ -10,9 +10,8 @@ use nginx_sys::{
     NGX_HTTP_MAIN_CONF, NGX_HTTP_MAIN_CONF_OFFSET, NGX_HTTP_MODULE, NGX_HTTP_VAR_CHANGEABLE,
     NGX_HTTP_VAR_NOCACHEABLE, NGX_LOG_EMERG,
 };
-use ngx::core::{
-    NgxStr, NgxString, Pool, RbTreeMap, SlabPool, Status, NGX_CONF_ERROR, NGX_CONF_OK,
-};
+use ngx::collections::RbTreeMap;
+use ngx::core::{NgxStr, NgxString, Pool, SlabPool, Status, NGX_CONF_ERROR, NGX_CONF_OK};
 use ngx::http::{HttpModule, HttpModuleMainConf};
 use ngx::{ngx_conf_log_error, ngx_log_debug, ngx_string};
 
diff --git a/src/allocator.rs b/src/allocator.rs
index 15fa4d6..685e428 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -11,10 +11,10 @@ use ::core::alloc::Layout;
 use ::core::mem;
 use ::core::ptr::{self, NonNull};
 
-pub use allocator_api2::alloc::{AllocError, Allocator, Global};
+pub use allocator_api2::alloc::{AllocError, Allocator};
 
 #[cfg(feature = "alloc")]
-pub use allocator_api2::{boxed, collections, vec};
+pub use allocator_api2::{alloc::Global, boxed::Box};
 
 /// Explicitly duplicate an object using the specified Allocator.
 pub trait TryCloneIn: Sized {
@@ -81,3 +81,24 @@ mod impls {
         }
     }
 }
+
+/// Allows turning a [`Box<T: Sized, A>`][Box] into a [`Box<U: ?Sized, A>`][Box] where `T` can be
+/// unsizing-coerced into a `U`.
+///
+/// See [allocator_api2::unsize_box] for an explanation why this macro is necessary.
+#[cfg(feature = "alloc")]
+#[doc(inline)]
+pub use crate::__unsize_box as unsize_box;
+
+// We have to reimplement this macro because the original implementation is not reexportable.
+// Macro definitions float to the top of the crate, thus we also mark it as hidden and reexport
+// again from the right namespace.
+#[cfg(feature = "alloc")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __unsize_box {
+    ( $boxed:expr $(,)? ) => {{
+        let (ptr, alloc) = $crate::allocator::Box::into_raw_with_allocator($boxed);
+        unsafe { $crate::allocator::Box::from_raw_in(ptr as *mut _, alloc) }
+    }};
+}
diff --git a/src/collections/mod.rs b/src/collections/mod.rs
new file mode 100644
index 0000000..5689cd0
--- /dev/null
+++ b/src/collections/mod.rs
@@ -0,0 +1,15 @@
+//! Collection types.
+//!
+//! This module provides common collection types, mostly implemented as wrappers over the
+//! corresponding NGINX types.
+
+#[cfg(feature = "alloc")]
+pub use allocator_api2::{
+    collections::{TryReserveError, TryReserveErrorKind},
+    vec, // reexport both the module and the macro
+    vec::Vec,
+};
+
+pub use rbtree::RbTreeMap;
+
+pub mod rbtree;
diff --git a/src/core/rbtree.rs b/src/collections/rbtree.rs
similarity index 100%
rename from src/core/rbtree.rs
rename to src/collections/rbtree.rs
diff --git a/src/core/mod.rs b/src/core/mod.rs
index 31768df..ad8264c 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -1,13 +1,11 @@
 mod buffer;
 mod pool;
-pub mod rbtree;
 pub mod slab;
 mod status;
 mod string;
 
 pub use buffer::*;
 pub use pool::*;
-pub use rbtree::RbTreeMap;
 pub use slab::SlabPool;
 pub use status::*;
 pub use string::*;
diff --git a/src/core/string.rs b/src/core/string.rs
index 48bf042..c43b994 100644
--- a/src/core/string.rs
+++ b/src/core/string.rs
@@ -207,9 +207,8 @@ mod _alloc {
 
     use super::*;
 
-    use crate::allocator::collections::TryReserveError;
-    use crate::allocator::vec::Vec;
     use crate::allocator::{self, Allocator};
+    use crate::collections::{TryReserveError, Vec};
 
     /// Owned byte string type with Allocator support.
     ///
diff --git a/src/lib.rs b/src/lib.rs
index 0dd4fc3..6bc96a0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -43,6 +43,7 @@ extern crate std;
 pub mod allocator;
 #[cfg(feature = "async")]
 pub mod async_;
+pub mod collections;
 
 /// The core module.
 ///