diff --git a/src/modelseed_api/services/genome_annotator.py b/src/modelseed_api/services/genome_annotator.py
index ce07acd..594b52c 100644
--- a/src/modelseed_api/services/genome_annotator.py
+++ b/src/modelseed_api/services/genome_annotator.py
@@ -183,6 +183,8 @@ def annotate_fasta(
                 [genome_dict, {"stages": stages}],
             )
             break
+        except TypeError as exc:
+            raise RuntimeError("RAST malformed error response (expected dict, got str). Original: " + str(exc)) from exc
         except Exception as exc:
             msg = str(exc)
             is_transient = any(code in msg for code in _TRANSIENT_5XX)
diff --git a/tests/unit/test_genome_annotator.py b/tests/unit/test_genome_annotator.py
index 558c518..7a1e181 100644
--- a/tests/unit/test_genome_annotator.py
+++ b/tests/unit/test_genome_annotator.py
@@ -178,3 +178,20 @@ def call(self, method, params):
 
         with pytest.raises(ValueError, match="no.*functional roles"):
             annotate_fasta(">p1\nMKKLVAVLIVSLAVALSALAVA")
+
+
+
+class TestAnnotateFastaTypeErrorHandling:
+    def test_rpc_typeerror_wraps_to_runtimeerror(self, monkeypatch):
+        class BadErrorClient:
+            def __init__(self, url, timeout=600):
+                pass
+            def call(self, method, params):
+                raise TypeError(
+                    "argument after ** must be a mapping, not str"
+                )
+        monkeypatch.setattr(
+            "modelseed_api.services.genome_annotator.RPCClient", BadErrorClient,
+        )
+        with pytest.raises(RuntimeError, match="malformed error response"):
+            annotate_fasta(">p1\nMKKLVAVLIVSLAVALSALAVA")
\ No newline at end of file