diff --git a/src/aead/algorithm.rs b/src/aead/algorithm.rs
index ee8e4da1c..2f1690292 100644
--- a/src/aead/algorithm.rs
+++ b/src/aead/algorithm.rs
@@ -12,7 +12,11 @@
 // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-use crate::{constant_time, cpu, error, hkdf};
+use crate::{
+    constant_time, cpu,
+    error::{self, InputTooLongError},
+    hkdf,
+};
 use core::ops::RangeFrom;
 
 use super::{
@@ -246,6 +250,7 @@ fn chacha20_poly1305_seal(
         _ => unreachable!(),
     };
     chacha20_poly1305::seal(key, nonce, aad, in_out, cpu_features)
+        .map_err(error::erase::<InputTooLongError>)
 }
 
 fn chacha20_poly1305_open(
@@ -262,4 +267,5 @@ fn chacha20_poly1305_open(
     };
     let in_out = Overlapping::new(in_out, src).map_err(error::erase::<SrcIndexError>)?;
     chacha20_poly1305::open(key, nonce, aad, in_out, cpu_features)
+        .map_err(error::erase::<InputTooLongError>)
 }
diff --git a/src/aead/chacha20_poly1305.rs b/src/aead/chacha20_poly1305.rs
index 2e84612a0..cb4e839ba 100644
--- a/src/aead/chacha20_poly1305.rs
+++ b/src/aead/chacha20_poly1305.rs
@@ -17,7 +17,8 @@ use super::{
     poly1305, Aad, Nonce, Tag,
 };
 use crate::{
-    cpu, error,
+    cpu,
+    error::InputTooLongError,
     polyfill::{u64_from_usize, usize_from_u64_saturated},
 };
 
@@ -43,11 +44,11 @@ pub(super) fn seal(
     aad: Aad<&[u8]>,
     in_out: &mut [u8],
     cpu_features: cpu::Features,
-) -> Result<Tag, error::Unspecified> {
+) -> Result<Tag, InputTooLongError> {
     let Key(chacha20_key) = key;
 
     if in_out.len() > MAX_IN_OUT_LEN {
-        return Err(error::Unspecified);
+        return Err(InputTooLongError::new(in_out.len()));
     }
     /// RFC 8439 Section 2.8 says the maximum AAD length is 2**64 - 1, which is
     /// never larger than usize::MAX, so we don't need an explicit length
@@ -127,11 +128,11 @@ pub(super) fn open(
     aad: Aad<&[u8]>,
     in_out: Overlapping<'_>,
     cpu_features: cpu::Features,
-) -> Result<Tag, error::Unspecified> {
+) -> Result<Tag, InputTooLongError> {
     let Key(chacha20_key) = key;
 
     if in_out.len() > MAX_IN_OUT_LEN {
-        return Err(error::Unspecified);
+        return Err(InputTooLongError::new(in_out.len()));
     }
     // RFC 8439 Section 2.8 says the maximum AAD length is 2**64 - 1, which is
     // never larger than usize::MAX, so we don't need an explicit length