diff --git a/Cargo.toml b/Cargo.toml
index db18ff4d..5298527d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,3 +1,3 @@
 [workspace]
-members = ["bitcoin"]
+members = ["bitcoin", "internals"]
 exclude = ["embedded", "fuzz"]
diff --git a/bitcoin/Cargo.toml b/bitcoin/Cargo.toml
index 0a371932..e8717845 100644
--- a/bitcoin/Cargo.toml
+++ b/bitcoin/Cargo.toml
@@ -25,7 +25,7 @@ secp-recovery = ["secp256k1/recovery"]
 # The no-std feature doesn't disable std - you need to turn off the std feature for that by disabling default.
 # Instead no-std enables additional features required for this crate to be usable without std.
 # As a result, both can be enabled without conflict.
-std = ["secp256k1/std", "bitcoin_hashes/std", "bech32/std"]
+std = ["secp256k1/std", "bitcoin_hashes/std", "bech32/std", "bitcoin-internals/std"]
 no-std = ["hashbrown", "core2/alloc", "bitcoin_hashes/alloc", "secp256k1/alloc"]
 
 [package.metadata.docs.rs]
@@ -33,6 +33,7 @@ features = [ "std", "secp-recovery", "base64", "rand", "serde", "bitcoinconsensu
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
+bitcoin-internals = { path = "../internals" }
 bech32 = { version = "0.9.0", default-features = false }
 bitcoin_hashes = { version = "0.11.0", default-features = false }
 secp256k1 = { version = "0.24.0", default-features = false, features = ["bitcoin_hashes"] }
diff --git a/bitcoin/src/address.rs b/bitcoin/src/address.rs
index 60aaaa80..5534e263 100644
--- a/bitcoin/src/address.rs
+++ b/bitcoin/src/address.rs
@@ -27,6 +27,7 @@ use core::fmt;
 use core::str::FromStr;
 
 use bech32;
+use bitcoin_internals::write_err;
 use secp256k1::{Secp256k1, Verification, XOnlyPublicKey};
 
 use crate::blockdata::constants::{
@@ -38,7 +39,7 @@ use crate::blockdata::{opcodes, script};
 use crate::error::ParseIntError;
 use crate::hash_types::{PubkeyHash, ScriptHash};
 use crate::hashes::{sha256, Hash, HashEngine};
-use crate::internal_macros::{serde_string_impl, write_err};
+use crate::internal_macros::serde_string_impl;
 use crate::network::constants::Network;
 use crate::prelude::*;
 use crate::util::base58;
diff --git a/bitcoin/src/bip158.rs b/bitcoin/src/bip158.rs
index 25fa0d8a..7692d5a2 100644
--- a/bitcoin/src/bip158.rs
+++ b/bitcoin/src/bip158.rs
@@ -42,6 +42,8 @@
 use core::cmp::{self, Ordering};
 use core::fmt::{self, Display, Formatter};
 
+use bitcoin_internals::write_err;
+
 use crate::blockdata::block::Block;
 use crate::blockdata::script::Script;
 use crate::blockdata::transaction::OutPoint;
@@ -49,7 +51,6 @@ use crate::consensus::encode::VarInt;
 use crate::consensus::{Decodable, Encodable};
 use crate::hash_types::{BlockHash, FilterHash, FilterHeader};
 use crate::hashes::{siphash24, Hash};
-use crate::internal_macros::write_err;
 use crate::io;
 use crate::prelude::*;
 use crate::util::endian;
@@ -273,7 +274,8 @@ impl GcsFilterReader {
         let reader = &mut decoder;
         // map hashes to [0, n_elements << grp]
         let nm = n_elements.0 * self.m;
-        let mut mapped = query.map(|e| map_to_range(self.filter.hash(e.borrow()), nm)).collect::<Vec<_>>();
+        let mut mapped =
+            query.map(|e| map_to_range(self.filter.hash(e.borrow()), nm)).collect::<Vec<_>>();
         // sort
         mapped.sort_unstable();
         if mapped.is_empty() {
@@ -317,7 +319,8 @@ impl GcsFilterReader {
         let reader = &mut decoder;
         // map hashes to [0, n_elements << grp]
         let nm = n_elements.0 * self.m;
-        let mut mapped = query.map(|e| map_to_range(self.filter.hash(e.borrow()), nm)).collect::<Vec<_>>();
+        let mut mapped =
+            query.map(|e| map_to_range(self.filter.hash(e.borrow()), nm)).collect::<Vec<_>>();
         // sort
         mapped.sort_unstable();
         mapped.dedup();
diff --git a/bitcoin/src/blockdata/locktime/absolute.rs b/bitcoin/src/blockdata/locktime/absolute.rs
index 0bc4c441..8543a808 100644
--- a/bitcoin/src/blockdata/locktime/absolute.rs
+++ b/bitcoin/src/blockdata/locktime/absolute.rs
@@ -12,11 +12,12 @@ use core::cmp::{PartialOrd, Ordering};
 use core::convert::TryFrom;
 use core::str::FromStr;
 
+use bitcoin_internals::write_err;
+
 use crate::consensus::encode::{self, Decodable, Encodable};
 use crate::error::ParseIntError;
 use crate::io::{self, Read, Write};
 use crate::prelude::*;
-use crate::internal_macros::write_err;
 use crate::parse::{self, impl_parse_str_through_int};
 
 /// The Threshold for deciding whether a lock time value is a height or a time (see [Bitcoin Core]).
diff --git a/bitcoin/src/blockdata/script.rs b/bitcoin/src/blockdata/script.rs
index 4ac3e71a..11be7899 100644
--- a/bitcoin/src/blockdata/script.rs
+++ b/bitcoin/src/blockdata/script.rs
@@ -20,7 +20,7 @@ use core::{fmt, default::Default};
 use core::ops::Index;
 use crate::internal_macros::debug_from_display;
 #[cfg(feature = "bitcoinconsensus")]
-use crate::internal_macros::write_err;
+use bitcoin_internals::write_err;
 
 #[cfg(feature = "serde")] use serde;
 
diff --git a/bitcoin/src/blockdata/transaction.rs b/bitcoin/src/blockdata/transaction.rs
index 7a0dd151..3b499df7 100644
--- a/bitcoin/src/blockdata/transaction.rs
+++ b/bitcoin/src/blockdata/transaction.rs
@@ -18,6 +18,8 @@ use crate::io;
 use core::{fmt, str, default::Default};
 use core::convert::TryFrom;
 
+use bitcoin_internals::write_err;
+
 use crate::hashes::{self, Hash, sha256d};
 use crate::hashes::hex::FromHex;
 
@@ -30,7 +32,7 @@ use crate::blockdata::locktime::relative;
 use crate::consensus::{encode, Decodable, Encodable};
 use crate::hash_types::{Sighash, Txid, Wtxid};
 use crate::VarInt;
-use crate::internal_macros::{impl_consensus_encoding, serde_struct_human_string_impl, write_err};
+use crate::internal_macros::{impl_consensus_encoding, serde_struct_human_string_impl};
 use crate::parse::impl_parse_str_through_int;
 
 #[cfg(doc)]
diff --git a/bitcoin/src/consensus/encode.rs b/bitcoin/src/consensus/encode.rs
index e2997225..e1afd10a 100644
--- a/bitcoin/src/consensus/encode.rs
+++ b/bitcoin/src/consensus/encode.rs
@@ -20,9 +20,10 @@ use crate::prelude::*;
 
 use core::{fmt, mem, u32, convert::From};
 
+use bitcoin_internals::write_err;
+
 use crate::hashes::{sha256d, Hash, sha256};
 use crate::hash_types::{BlockHash, FilterHash, TxMerkleNode, FilterHeader};
-use crate::internal_macros::write_err;
 use crate::io::{self, Cursor, Read};
 
 use crate::util::endian;
diff --git a/bitcoin/src/internal_macros.rs b/bitcoin/src/internal_macros.rs
index 2e8835ce..bc196c6c 100644
--- a/bitcoin/src/internal_macros.rs
+++ b/bitcoin/src/internal_macros.rs
@@ -626,26 +626,6 @@ macro_rules! user_enum {
 }
 pub(crate) use user_enum;
 
-/// Formats error. If `std` feature is OFF appends error source (delimited by `: `). We do this
-/// because `e.source()` is only available in std builds, without this macro the error source is
-/// lost for no-std builds.
-macro_rules! write_err {
-    ($writer:expr, $string:literal $(, $args:expr)*; $source:expr) => {
-        {
-            #[cfg(feature = "std")]
-            {
-                let _ = &$source;   // Prevents clippy warnings.
-                write!($writer, $string $(, $args)*)
-            }
-            #[cfg(not(feature = "std"))]
-            {
-                write!($writer, concat!($string, ": {}") $(, $args)*, $source)
-            }
-        }
-    }
-}
-pub(crate) use write_err;
-
 /// Asserts a boolean expression at compile time.
 macro_rules! const_assert {
     ($x:expr) => {{
diff --git a/bitcoin/src/parse.rs b/bitcoin/src/parse.rs
index 3b352d15..fd69cbf2 100644
--- a/bitcoin/src/parse.rs
+++ b/bitcoin/src/parse.rs
@@ -2,8 +2,9 @@ use core::convert::TryFrom;
 use core::fmt;
 use core::str::FromStr;
 
+use bitcoin_internals::write_err;
+
 use crate::error::impl_std_error;
-use crate::internal_macros::write_err;
 use crate::prelude::*;
 
 /// Error with rich context returned when a string can't be parsed as an integer.
diff --git a/bitcoin/src/util/base58.rs b/bitcoin/src/util/base58.rs
index d548f116..7fcc78a8 100644
--- a/bitcoin/src/util/base58.rs
+++ b/bitcoin/src/util/base58.rs
@@ -11,11 +11,11 @@ use crate::prelude::*;
 
 use core::{fmt, str, iter, slice};
 
+use bitcoin_internals::write_err;
 use crate::hashes::{sha256d, Hash, hex};
 use secp256k1;
 
 use crate::util::{endian, key};
-use crate::internal_macros::write_err;
 
 /// An error that might occur during base58 decoding
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone)]
diff --git a/bitcoin/src/util/bip32.rs b/bitcoin/src/util/bip32.rs
index 9f18916d..a6d1a17c 100644
--- a/bitcoin/src/util/bip32.rs
+++ b/bitcoin/src/util/bip32.rs
@@ -14,6 +14,7 @@ use core::{fmt, str::FromStr, default::Default};
 use core::ops::Index;
 #[cfg(feature = "serde")] use serde;
 
+use bitcoin_internals::write_err;
 use crate::hash_types::XpubIdentifier;
 use crate::hashes::{sha512, Hash, HashEngine, Hmac, HmacEngine, hex};
 use secp256k1::{self, Secp256k1, XOnlyPublicKey};
@@ -21,7 +22,7 @@ use secp256k1::{self, Secp256k1, XOnlyPublicKey};
 use crate::network::constants::Network;
 use crate::util::{base58, endian, key};
 use crate::util::key::{PublicKey, PrivateKey, KeyPair};
-use crate::internal_macros::{impl_array_newtype, impl_bytes_newtype, serde_string_impl, write_err};
+use crate::internal_macros::{impl_array_newtype, impl_bytes_newtype, serde_string_impl};
 
 /// A chain code
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
diff --git a/bitcoin/src/util/ecdsa.rs b/bitcoin/src/util/ecdsa.rs
index 50116723..682ab298 100644
--- a/bitcoin/src/util/ecdsa.rs
+++ b/bitcoin/src/util/ecdsa.rs
@@ -8,11 +8,11 @@
 use core::str::FromStr;
 use core::{fmt, iter};
 
+use bitcoin_internals::write_err;
 use secp256k1;
 
 use crate::prelude::*;
 use crate::hashes::hex::{self, FromHex};
-use crate::internal_macros::write_err;
 use crate::util::sighash::{EcdsaSighashType, NonStandardSighashType};
 
 /// An ECDSA signature with the corresponding hash type.
diff --git a/bitcoin/src/util/key.rs b/bitcoin/src/util/key.rs
index ffc1c2e5..c53d648f 100644
--- a/bitcoin/src/util/key.rs
+++ b/bitcoin/src/util/key.rs
@@ -11,6 +11,7 @@ use crate::prelude::*;
 use core::{ops, str::FromStr};
 use core::fmt::{self, Write};
 
+use bitcoin_internals::write_err;
 pub use secp256k1::{self, Secp256k1, XOnlyPublicKey, KeyPair};
 
 use crate::io;
@@ -18,7 +19,6 @@ use crate::network::constants::Network;
 use crate::hashes::{Hash, hash160, hex, hex::FromHex};
 use crate::hash_types::{PubkeyHash, WPubkeyHash};
 use crate::util::base58;
-use crate::internal_macros::write_err;
 
 /// A key-related error.
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
diff --git a/bitcoin/src/util/misc.rs b/bitcoin/src/util/misc.rs
index dea34063..fc1807ca 100644
--- a/bitcoin/src/util/misc.rs
+++ b/bitcoin/src/util/misc.rs
@@ -27,13 +27,13 @@ mod message_signing {
 
     use core::fmt;
 
+    use bitcoin_internals::write_err;
     use crate::hashes::sha256d;
     use secp256k1;
     use secp256k1::ecdsa::{RecoveryId, RecoverableSignature};
 
     use crate::util::key::PublicKey;
     use crate::address::{Address, AddressType};
-    use crate::internal_macros::write_err;
 
     /// An error used for dealing with Bitcoin Signed Messages.
     #[cfg_attr(docsrs, doc(cfg(feature = "secp-recovery")))]
diff --git a/bitcoin/src/util/mod.rs b/bitcoin/src/util/mod.rs
index 52f61ecd..72d66095 100644
--- a/bitcoin/src/util/mod.rs
+++ b/bitcoin/src/util/mod.rs
@@ -28,8 +28,9 @@ use crate::prelude::*;
 use crate::io;
 use core::fmt;
 
+use bitcoin_internals::write_err;
+
 use crate::consensus::encode;
-use crate::internal_macros::write_err;
 
 /// A trait which allows numbers to act as fixed-size bit arrays
 pub trait BitArray {
diff --git a/bitcoin/src/util/psbt/error.rs b/bitcoin/src/util/psbt/error.rs
index 7965e0e6..4424a809 100644
--- a/bitcoin/src/util/psbt/error.rs
+++ b/bitcoin/src/util/psbt/error.rs
@@ -4,13 +4,14 @@ use crate::prelude::*;
 
 use core::fmt;
 
+use bitcoin_internals::write_err;
+
 use crate::blockdata::transaction::Transaction;
 use crate::consensus::encode;
 use crate::util::psbt::raw;
 
 use crate::hashes;
 use crate::util::bip32::ExtendedPubKey;
-use crate::internal_macros::write_err;
 
 /// Enum for marking psbt hash error.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
diff --git a/bitcoin/src/util/psbt/mod.rs b/bitcoin/src/util/psbt/mod.rs
index 6e88bd39..99b328ad 100644
--- a/bitcoin/src/util/psbt/mod.rs
+++ b/bitcoin/src/util/psbt/mod.rs
@@ -207,7 +207,7 @@ mod display_from_str {
     use core::str::FromStr;
     use crate::consensus::encode::{Error, self};
     use base64::display::Base64Display;
-    use crate::internal_macros::write_err;
+    use bitcoin_internals::write_err;
 
     /// Error encountered during PSBT decoding from Base64 string.
     #[derive(Debug)]
diff --git a/bitcoin/src/util/schnorr.rs b/bitcoin/src/util/schnorr.rs
index 81729e17..7036b6a2 100644
--- a/bitcoin/src/util/schnorr.rs
+++ b/bitcoin/src/util/schnorr.rs
@@ -9,12 +9,13 @@
 
 use core::fmt;
 
+use bitcoin_internals::write_err;
+
 use crate::prelude::*;
 
 use secp256k1::{self, Secp256k1, Verification, constants};
 use crate::util::taproot::{TapBranchHash, TapTweakHash};
 use crate::SchnorrSighashType;
-use crate::internal_macros::write_err;
 
 /// Deprecated re-export of [`secp256k1::XOnlyPublicKey`]
 #[deprecated(since = "0.28.0", note = "Please use `util::key::XOnlyPublicKey` instead")]
diff --git a/bitcoin/src/util/taproot.rs b/bitcoin/src/util/taproot.rs
index 7e7f9190..7e37e2e3 100644
--- a/bitcoin/src/util/taproot.rs
+++ b/bitcoin/src/util/taproot.rs
@@ -7,6 +7,7 @@
 
 use crate::prelude::*;
 use crate::io;
+use bitcoin_internals::write_err;
 use secp256k1::{self, Secp256k1, Scalar};
 
 use core::convert::TryFrom;
@@ -17,7 +18,6 @@ use crate::hashes::{sha256, sha256t_hash_newtype, Hash, HashEngine};
 use crate::schnorr::{TweakedPublicKey, UntweakedPublicKey, TapTweak};
 use crate::util::key::XOnlyPublicKey;
 use crate::Script;
-use crate::internal_macros::write_err;
 use crate::consensus::Encodable;
 
 /// The SHA-256 midstate value for the TapLeaf hash.
diff --git a/internals/Cargo.toml b/internals/Cargo.toml
new file mode 100644
index 00000000..f23271f6
--- /dev/null
+++ b/internals/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+name = "bitcoin-internals"
+version = "0.1.0"
+authors = ["Andrew Poelstra <apoelstra@wpsoftware.net>", "The Rust Bitcoin developers"]
+license = "CC0-1.0"
+repository = "https://github.com/rust-bitcoin/rust-bitcoin/"
+documentation = "https://docs.rs/bitcoin-internals"
+description = "Internal types and macros used by rust-bitcoin ecosystem"
+categories = ["cryptography::cryptocurrencies"]
+keywords = ["internal"]
+readme = "README.md"
+edition = "2018"
+
+# Please don't forget to add relevant features to docs.rs below.
+[features]
+default = []
+std = []
+
+[package.metadata.docs.rs]
+features = ["std"]
+rustdoc-args = ["--cfg", "docsrs"]
+
+[dependencies]
+
+[dev-dependencies]
diff --git a/internals/README.md b/internals/README.md
new file mode 100644
index 00000000..79aa2980
--- /dev/null
+++ b/internals/README.md
@@ -0,0 +1,7 @@
+Rust Bitcoin Internals
+======================
+
+This crate is only meant to be used internally by crates in the
+[rust-bitcoin](https://github.com/rust-bitcoin) ecosystem.
+
+This crate will never be stabilized, depend on it at your own risk.
diff --git a/internals/src/error.rs b/internals/src/error.rs
new file mode 100644
index 00000000..2f213377
--- /dev/null
+++ b/internals/src/error.rs
@@ -0,0 +1,29 @@
+// Written by the Rust Bitcoin developers.
+// SPDX-License-Identifier: CC0-1.0
+
+//! # Error
+//!
+//! Error handling macros and helpers.
+//!
+
+/// Formats error.
+///
+/// If `std` feature is OFF appends error source (delimited by `: `). We do this because
+/// `e.source()` is only available in std builds, without this macro the error source is lost for
+/// no-std builds.
+#[macro_export]
+macro_rules! write_err {
+    ($writer:expr, $string:literal $(, $args:expr)*; $source:expr) => {
+        {
+            #[cfg(feature = "std")]
+            {
+                let _ = &$source;   // Prevents clippy warnings.
+                write!($writer, $string $(, $args)*)
+            }
+            #[cfg(not(feature = "std"))]
+            {
+                write!($writer, concat!($string, ": {}") $(, $args)*, $source)
+            }
+        }
+    }
+}
diff --git a/internals/src/lib.rs b/internals/src/lib.rs
new file mode 100644
index 00000000..bad0d8d2
--- /dev/null
+++ b/internals/src/lib.rs
@@ -0,0 +1,24 @@
+// Written by the Rust Bitcoin developers.
+// SPDX-License-Identifier: CC0-1.0
+
+//! # Rust Bitcoin Internal
+//!
+//! This crate is only meant to be used internally by crates in the
+//! [rust-bitcoin](https://github.com/rust-bitcoin) ecosystem.
+//!
+
+#![cfg_attr(all(not(feature = "std"), not(test)), no_std)]
+// Experimental features we need.
+#![cfg_attr(docsrs, feature(doc_cfg))]
+// Coding conventions
+#![forbid(unsafe_code)]
+#![deny(non_upper_case_globals)]
+#![deny(non_camel_case_types)]
+#![deny(non_snake_case)]
+#![deny(unused_mut)]
+#![deny(dead_code)]
+#![deny(unused_imports)]
+#![deny(missing_docs)]
+#![deny(unused_must_use)]
+
+pub mod error;