diff --git a/src/schema/nmdc.yaml b/src/schema/nmdc.yaml
index 0d2c24b2cf..78c4f98027 100644
--- a/src/schema/nmdc.yaml
+++ b/src/schema/nmdc.yaml
@@ -536,8 +536,6 @@ classes:
           expected_value:
             tag: expected_value
             value: date string
-        is_a: attribute
-        multivalued: false
         range: string
       flooding:
         annotations: