diff --git a/CHANGELOG.md b/CHANGELOG.md
index adf1d1c..1ef083a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,9 @@
 - resfinder_curation: grdA_1_QJX10702 -> 3007380 & EstDL136_1_JN242251 -> 3000557
 - megares_curation: MEG_2865|Drugs|Phenicol|Chloramphenicol_hydrolase|ESTD -> 3000557
 
+### Handle AROs as string rather than int in get_aro_mapping_table()
+AROs were previously handled as 'int' in the get_aro_mapping_table() function and this posed challenges when ARO numbers such as 'ARO:0010004' (leading zeros are cut). To fix this, AROs are now treated as strings so leading zeros can be maintained.
+
 ## 0.4.0 - 10 June
 
 - Bundle a specific version of ARO with the package instead of downloading it from the internet (ensures reproducibility)
diff --git a/argnorm/lib.py b/argnorm/lib.py
index 747ffed..88a8011 100644
--- a/argnorm/lib.py
+++ b/argnorm/lib.py
@@ -42,18 +42,18 @@ def get_aro_mapping_table(database):
 
     aro_mapping_table = pd.read_csv(
             os.path.join(_ROOT, 'data', f'{database}_ARO_mapping.tsv'),
-            sep='\t')
+            sep='\t', dtype={'ARO': str})
     aro_mapping_table.drop_duplicates(subset=['Original ID'], inplace=True)
     aro_mapping_table.set_index('Original ID', inplace=True)
 
     manual_curation = pd.read_csv(
                     os.path.join(_ROOT, 'data/manual_curation', f'{database}_curation.tsv'),
-                    sep='\t', index_col=0)
+                    sep='\t', index_col=0, dtype={'ARO': str})
     manual_curation['Database'] = aro_mapping_table['Database'].iloc[0]
     aro_mapping_table.drop(index=set(manual_curation.index) & set(aro_mapping_table.index), inplace=True)
     aro_mapping_table = pd.concat([aro_mapping_table, manual_curation])
 
-    aro_mapping_table['ARO'] = aro_mapping_table['ARO'].map(lambda a: f'ARO:{int(a)}', na_action='ignore')
+    aro_mapping_table['ARO'] = aro_mapping_table['ARO'].map(lambda a: f'ARO:{a}', na_action='ignore')
     return aro_mapping_table
 
 def map_to_aro(gene, database):
diff --git a/tests/test_lib.py b/tests/test_lib.py
index 893b96b..8422523 100644
--- a/tests/test_lib.py
+++ b/tests/test_lib.py
@@ -9,7 +9,8 @@ def test_map_to_aro():
         ["1028085756|WP_063844287.1|1|1|cpt|cpt|phosphotransferase|2|CHLORAMPHENICOL|PHENICOL|chloramphenicol_phosphotransferase_CPT", 'ncbi'],
         ["gb|AAG57600.1|ARO:3000318|mphB", "sarg"],
         ["(Phe)cpt_strepv:U09991:AAB36569:1412-1948:537", "argannot"],
-        ["MEG_4060|Metals|Multi-metal_resistance|Multi-metal_resistance_protein|MREA", "megares"]
+        ["MEG_4060|Metals|Multi-metal_resistance|Multi-metal_resistance_protein|MREA", "megares"],
+        ["gi:447201629:ref:WP_001278885.1:|FEATURES|cob(I)alamin_adenolsyltransferase|unclassified|cob(I)alamin_adenolsyltransferase", "deeparg"]
     ]
 
     ARO = lib.get_aro_ontology()
@@ -19,7 +20,8 @@ def test_map_to_aro():
         ARO.get_term('ARO:3000249'),
         ARO.get_term('ARO:3000318'),
         ARO.get_term('ARO:3000249'),
-        None
+        None,
+        ARO.get_term('ARO:0010004')
     ]
 
     for t, e in zip(test_cases, expected_output):