diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6076b631..dd54b8e3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Fixed
 
 - Correctly refer to input peak files by their full file path.
+- Specifying custom residues to retrain Casanovo is now possible.
 
 ## [3.3.0] - 2023-04-04
 
diff --git a/casanovo/config.py b/casanovo/config.py
index 4dc93c26..0dfdaf67 100644
--- a/casanovo/config.py
+++ b/casanovo/config.py
@@ -50,6 +50,7 @@ class Config:
         dropout=float,
         dim_intensity=int,
         max_length=int,
+        residues=dict,
         n_log=int,
         tb_summarywriter=str,
         warmup_iters=int,
diff --git a/tests/unit_tests/test_config.py b/tests/unit_tests/test_config.py
index 8282e367..89b37e42 100644
--- a/tests/unit_tests/test_config.py
+++ b/tests/unit_tests/test_config.py
@@ -1,6 +1,4 @@
 """Test configuration loading"""
-import pytest
-
 from casanovo.config import Config
 
 
@@ -17,11 +15,23 @@ def test_override(tmp_path):
     """Test overriding the default"""
     yml = tmp_path / "test.yml"
     with yml.open("w+") as f_out:
-        f_out.write("random_seed: 42\ntop_match: 3")
+        f_out.write(
+            """random_seed: 42
+top_match: 3
+residues:
+  W: 1
+  O: 2
+  U: 3
+  T: 4
+"""
+        )
 
     config = Config(yml)
     assert config.random_seed == 42
     assert config["random_seed"] == 42
     assert not config.no_gpu
     assert config.top_match == 3
+    assert len(config.residues) == 4
+    for i, residue in enumerate("WOUT", 1):
+        assert config["residues"][residue] == i
     assert config.file == str(yml)