diff --git a/recordprocessor/src/utils_for_fhir_conversion.py b/recordprocessor/src/utils_for_fhir_conversion.py
index 8e91ed63a5..ebc44a57d6 100644
--- a/recordprocessor/src/utils_for_fhir_conversion.py
+++ b/recordprocessor/src/utils_for_fhir_conversion.py
@@ -68,9 +68,9 @@ def date(date: str) -> str:
 
     @staticmethod
     def gender_code(code: any) -> any:
-        """Converts gender code to fhir gender if the code is recognised. Otherwise returns the original code."""
+        """Converts gender code to fhir gender if the code is recognised. Otherwise returns 'invalid'."""
         code_to_fhir = {"1": "male", "2": "female", "9": "other", "0": "unknown"}
-        return code_to_fhir.get(code, code)
+        return code_to_fhir.get(code, "invalid")
 
     @staticmethod
     def boolean(value: any) -> any:
diff --git a/recordprocessor/tests/test_utils_for_fhir_conversion.py b/recordprocessor/tests/test_utils_for_fhir_conversion.py
index 7b77b2ad56..01efd42a9d 100644
--- a/recordprocessor/tests/test_utils_for_fhir_conversion.py
+++ b/recordprocessor/tests/test_utils_for_fhir_conversion.py
@@ -88,8 +88,8 @@ def test_convert_gender_code(self):
             self.assertEqual(Convert.gender_code(code), expected)
 
         # Invalid gender codes
-        for value in [1, "invalid", None]:
-            self.assertEqual(Convert.gender_code(value), value)
+        for value in [1, "3", "1290", "male", "invalid", None]:
+            self.assertEqual(Convert.gender_code(value), "invalid")
 
     def test_convert_boolean(self):
         """