diff --git a/src/koza/io/writer/tsv_writer.py b/src/koza/io/writer/tsv_writer.py
index 9e9d6dc..8c1f79a 100644
--- a/src/koza/io/writer/tsv_writer.py
+++ b/src/koza/io/writer/tsv_writer.py
@@ -84,24 +84,22 @@ def get_new_fh_path(base_dir, filename, category):
         if split:
             base_dir, filename = Path(fh.name).parent, getattr(self, f"{record_type}s_file_name").name
             if record_type == "node":
-                category = record.get("category", ["UnknownNodeCategory"])[0].split(":")[-1]
+                category = record.get("category", [""])[0].split(":")[-1]
             else:
                 subject_category = (
-                    record.get("subject_category", "UnknownSubjectCategory").split(":")[-1]
+                    record.get("subject_category", "").split(":")[-1]
                     if record.get("subject_category")
-                    else "UnknownSubjectCategory"
+                    else "UnknownCategory"
                 )
 
                 object_category = (
-                    record.get("object_category", "UnknownObjectCategory").split(":")[-1]
+                    record.get("object_category", "").split(":")[-1]
                     if record.get("object_category")
-                    else "UnknownObjectCategory"
+                    else "UnknownCategory"
                 )
 
                 edge_category = (
-                    record.get("category", ["UnknownEdgeCategory"])[0].split(":")[-1]
-                    if record.get("category")
-                    else "UnknownEdgeCategory"
+                    record.get("category", [""])[0].split(":")[-1] if record.get("category") else "UnknownCategory"
                 )
 
                 category = subject_category + edge_category + object_category
diff --git a/tests/unit/test_tsvwriter_node_and_edge.py b/tests/unit/test_tsvwriter_node_and_edge.py
index c8d7d7f..692564f 100644
--- a/tests/unit/test_tsvwriter_node_and_edge.py
+++ b/tests/unit/test_tsvwriter_node_and_edge.py
@@ -40,8 +40,8 @@ def test_tsv_writer_split():
     """
     Writes a test tsv file
     """
-    g1 = Gene(id="HGNC:11603", name="TBX4")
-    d1 = Disease(id="MONDO:0005002", name="chronic obstructive pulmonary disease")
+    g1 = Gene(id="HGNC:11603", name="TBX4", category=["biolink:Gene"])
+    d1 = Disease(id="MONDO:0005002", name="chronic obstructive pulmonary disease", category=["biolink:Disease"])
     a1 = GeneToDiseaseAssociation(
         id="uuid:5b06e86f-d768-4cd9-ac27-abe31e95ab1e",
         subject=g1.id,
@@ -49,8 +49,10 @@ def test_tsv_writer_split():
         predicate="biolink:contributes_to",
         knowledge_level="not_provided",
         agent_type="not_provided",
+        subject_category="biolink:Gene",
+        object_category="biolink:Disease",
     )
-    g2 = Gene(id="HGNC:11604", name="TBX5")
+    g2 = Gene(id="HGNC:11604", name="TBX5", category=["biolink:Gene"])
     d2 = Disease(id="MONDO:0005003", name="asthma")
     a2 = GeneToDiseaseAssociation(
         id="uuid:5b06e86f-d768-4cd9-ac27-abe31e95ab1f",
@@ -61,7 +63,7 @@ def test_tsv_writer_split():
         agent_type="not_provided",
     )
     g3 = Gene(id="HGNC:11605", name="TBX6")
-    d3 = Disease(id="MONDO:0005004", name="lung cancer")
+    d3 = Disease(id="MONDO:0005004", name="lung cancer", category=["biolink:Disease"])
     a3 = GeneToDiseaseAssociation(
         id="uuid:5b06e86f-d768-4cd9-ac27-abe31e95ab1g",
         subject=g3.id,
@@ -70,14 +72,25 @@ def test_tsv_writer_split():
         knowledge_level="not_provided",
         agent_type="not_provided",
     )
-    ents = [[g1, d1, a1], [g2, d2, a2], [g3, d3, a3]]
+    g4 = Gene(id="HGNC:11606", name="TBX7")
+    d4 = Disease(id="MONDO:0005005", name="pulmonary fibrosis")
+    a4 = GeneToDiseaseAssociation(
+        id="uuid:5b06e86f-d768-4cd9-ac27-abe31e95ab1h",
+        subject=g4.id,
+        object=d4.id,
+        predicate="biolink:contributes_to",
+        knowledge_level="not_provided",
+        agent_type="not_provided",
+    )
+
+    ents = [[g1, d1, a1], [g2, d2, a2], [g3, d3, a3], [g4, d4, a4]]
 
     node_properties = ["id", "category", "symbol", "in_taxon", "provided_by", "source"]
     edge_properties = ["id", "subject", "predicate", "object", "category" "qualifiers", "publications", "provided_by"]
 
     outdir = "output/tests/split-examples"
     outfile = "tsvwriter"
-    split_edge_file_substring = "UnknownSubjectCategoryGeneToDiseaseAssociationUnknownObjectCategory"
+    split_edge_file_substring = "UnknownCategoryGeneToDiseaseAssociationUnknownCategory"
 
     t = TSVWriter(outdir, outfile, node_properties, edge_properties)
     for ent in ents: