diff --git a/api/io/all-features.txt b/api/io/all-features.txt
index 1a6cb4f7a..46b6a2935 100644
--- a/api/io/all-features.txt
+++ b/api/io/all-features.txt
@@ -1,6 +1,5 @@
 #[repr(transparent)] pub struct bitcoin_io::FromStd<T>(_)
 #[repr(transparent)] pub struct bitcoin_io::ToStd<T>(_)
-impl !core::marker::Sync for bitcoin_io::Error
 impl !core::panic::unwind_safe::RefUnwindSafe for bitcoin_io::Error
 impl !core::panic::unwind_safe::UnwindSafe for bitcoin_io::Error
 impl bitcoin_io::BufRead for &[u8]
@@ -70,6 +69,7 @@ impl core::marker::Send for bitcoin_io::Error
 impl core::marker::Send for bitcoin_io::ErrorKind
 impl core::marker::Send for bitcoin_io::Sink
 impl core::marker::StructuralPartialEq for bitcoin_io::ErrorKind
+impl core::marker::Sync for bitcoin_io::Error
 impl core::marker::Sync for bitcoin_io::ErrorKind
 impl core::marker::Sync for bitcoin_io::Sink
 impl core::marker::Unpin for bitcoin_io::Error
diff --git a/api/io/alloc-only.txt b/api/io/alloc-only.txt
index e0d9a76e5..5cb612794 100644
--- a/api/io/alloc-only.txt
+++ b/api/io/alloc-only.txt
@@ -1,4 +1,3 @@
-impl !core::marker::Sync for bitcoin_io::Error
 impl !core::panic::unwind_safe::RefUnwindSafe for bitcoin_io::Error
 impl !core::panic::unwind_safe::UnwindSafe for bitcoin_io::Error
 impl bitcoin_io::BufRead for &[u8]
@@ -28,6 +27,7 @@ impl core::marker::Send for bitcoin_io::Error
 impl core::marker::Send for bitcoin_io::ErrorKind
 impl core::marker::Send for bitcoin_io::Sink
 impl core::marker::StructuralPartialEq for bitcoin_io::ErrorKind
+impl core::marker::Sync for bitcoin_io::Error
 impl core::marker::Sync for bitcoin_io::ErrorKind
 impl core::marker::Sync for bitcoin_io::Sink
 impl core::marker::Unpin for bitcoin_io::Error
diff --git a/api/io/no-features.txt b/api/io/no-features.txt
index 3874ee8f7..493aab930 100644
--- a/api/io/no-features.txt
+++ b/api/io/no-features.txt
@@ -1,4 +1,3 @@
-impl !core::marker::Sync for bitcoin_io::Error
 impl !core::panic::unwind_safe::RefUnwindSafe for bitcoin_io::Error
 impl !core::panic::unwind_safe::UnwindSafe for bitcoin_io::Error
 impl bitcoin_io::BufRead for &[u8]
@@ -27,6 +26,7 @@ impl core::marker::Send for bitcoin_io::Error
 impl core::marker::Send for bitcoin_io::ErrorKind
 impl core::marker::Send for bitcoin_io::Sink
 impl core::marker::StructuralPartialEq for bitcoin_io::ErrorKind
+impl core::marker::Sync for bitcoin_io::Error
 impl core::marker::Sync for bitcoin_io::ErrorKind
 impl core::marker::Sync for bitcoin_io::Sink
 impl core::marker::Unpin for bitcoin_io::Error
diff --git a/io/src/error.rs b/io/src/error.rs
index 6ef943e42..ae5b5e44a 100644
--- a/io/src/error.rs
+++ b/io/src/error.rs
@@ -6,10 +6,12 @@ use core::fmt;
 #[derive(Debug)]
 pub struct Error {
     kind: ErrorKind,
-    /// Indicates that the `struct` can pretend to own a mutable static reference
-    /// and an [`UnsafeCell`](core::cell::UnsafeCell), which are not unwind safe.
-    /// This is so that it does not introduce non-additive cargo features.
-    _not_unwind_safe: core::marker::PhantomData<(&'static mut (), core::cell::UnsafeCell<()>)>,
+    /// We want this type to be `?UnwindSafe` and `?RefUnwindSafe` - the same as `std::io::Error`.
+    ///
+    /// In `std` builds the existence of `dyn std::error:Error` prevents `UnwindSafe` and
+    /// `RefUnwindSafe` from being automatically implemented. But in `no-std` builds without the
+    /// marker nothing prevents it.
+    _not_unwind_safe: core::marker::PhantomData<NotUnwindSafe>,
 
     #[cfg(feature = "std")]
     error: Option<Box<dyn std::error::Error + Send + Sync + 'static>>,
@@ -100,6 +102,13 @@ impl From<Error> for std::io::Error {
     }
 }
 
+/// Useful for preventing `UnwindSafe` and `RefUnwindSafe` from being automatically implemented.
+struct NotUnwindSafe {
+    _not_unwind_safe: core::marker::PhantomData<(&'static mut (), core::cell::UnsafeCell<()>)>,
+}
+
+unsafe impl Sync for NotUnwindSafe {}
+
 macro_rules! define_errorkind {
     ($($(#[$($attr:tt)*])* $kind:ident),*) => {
         #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
diff --git a/io/tests/api.rs b/io/tests/api.rs
index 608969c02..efc64f2e6 100644
--- a/io/tests/api.rs
+++ b/io/tests/api.rs
@@ -137,4 +137,8 @@ fn all_non_error_tyes_implement_send_sync() {
     //  Types are `Send` and `Sync` where possible (C-SEND-SYNC).
     assert_send::<Types>();
     assert_sync::<Types>();
+
+    // Error types are meaningful and well-behaved (C-GOOD-ERR)
+    assert_send::<Errors>();
+    assert_sync::<Errors>();
 }