OData - metadata returns primary key with attribute "Nullable=true"

<vdb name="test" version="1">
    <model name="Source" type="PHYSICAL">
        <source name="rs" connection-jndi-name="java:/Redshift" translator-name="postgresql"/>
        <metadata type="DDL">
            <![CDATA[create foreign table SmallB (
                IntKey integer PRIMARY KEY OPTIONS(NAMEINSOURCE 'intkey', NATIVE_TYPE 'int4')) OPTIONS(NAMEINSOURCE 'smalla');
            ]]>
        </metadata>
    </model>
</vdb>

<edmx:Edmx xmlns:edmx="http://schemas.microsoft.com/ado/2007/06/edmx" Version="1.0">
  <edmx:DataServices xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" m:DataServiceVersion="2.0">
    <Schema xmlns="http://schemas.microsoft.com/ado/2008/09/edm" Namespace="Source">
      <EntityType Name="SmallB">
        <Key>
          <PropertyRef Name="IntKey"/>
        </Key>
        <Property Name="IntKey" Type="Edm.Int32" Nullable="true"/>
      </EntityType>
      <EntityContainer Name="Source" m:IsDefaultEntityContainer="false">
        <EntitySet Name="SmallB" EntityType="Source.SmallB"/>
      </EntityContainer>
    </Schema>
...