diff --git a/litellm/llms/anthropic/wif.py b/litellm/llms/anthropic/wif.py
index 6b88bfd7f63..f490ad4938f 100644
--- a/litellm/llms/anthropic/wif.py
+++ b/litellm/llms/anthropic/wif.py
@@ -141,7 +141,9 @@ def _resolve_identity_source(
     if source_kind is None:
         legacy_ref: Final = _resolve_assertion_ref(litellm_params)
         return (legacy_ref, None) if legacy_ref is not None else None
-    params: Final = litellm_params if litellm_params is not None else _EMPTY_PARAMS
+    params: Final[Mapping[str, object]] = MappingProxyType(
+        {key: value for key, value in (litellm_params or _EMPTY_PARAMS).items() if value is not None}
+    )
     match source_kind:
         case AnthropicIdentitySourceKind.internal_issuer.value:
             _reject_foreign_variant_fields(params, foreign_field_map=_KEYCLOAK_FIELD_MAP, chosen_kind=source_kind)
diff --git a/tests/test_litellm/llms/anthropic/test_anthropic_wif.py b/tests/test_litellm/llms/anthropic/test_anthropic_wif.py
index 12b11dbc95f..db9fc50c09f 100644
--- a/tests/test_litellm/llms/anthropic/test_anthropic_wif.py
+++ b/tests/test_litellm/llms/anthropic/test_anthropic_wif.py
@@ -25,6 +25,7 @@ from litellm.llms.base_llm.auth.identity_source import (
 )
 from litellm.llms.base_llm.auth.jwt_signing import build_jwks, rfc7638_thumbprint
 from litellm.llms.base_llm.auth.token_exchange import JwtBearerTokenExchangeEngine
+from litellm.types.router import GenericLiteLLMParams
 from litellm.llms.base_llm.auth.types import (
     AssertionSourceError,
     ExchangeError,
@@ -930,6 +931,23 @@ class TestKeycloakIdentitySourceDispatch:
         assert first.assertion_ref != second.assertion_ref
 
 
+
+@pytest.mark.parametrize(
+    "sparse_params",
+    [TestInternalIssuerIdentitySourceDispatch.LITELLM_PARAMS, TestKeycloakIdentitySourceDispatch.LITELLM_PARAMS],
+    ids=["internal_issuer", "keycloak"],
+)
+def test_dense_router_params_dump_resolves_like_the_sparse_config(sparse_params: Mapping[str, object]):
+    dense_params = dict(GenericLiteLLMParams(**sparse_params))
+    assert any(value is None for value in dense_params.values())
+
+    dense = resolve_anthropic_wif_params(dense_params)
+    sparse = resolve_anthropic_wif_params(sparse_params)
+
+    assert dense is not None and sparse is not None
+    assert dense.assertion_ref == sparse.assertion_ref
+
+
 class TestIdentitySourceValidationFailsClosed:
     """Unknown discriminator, a missing required variant field, and a field belonging to the
     other variant are all hard config errors at resolution time -- never a silent fallback to