diff --git a/velox/functions/prestosql/aggregates/ApproxDistinctAggregate.cpp b/velox/functions/prestosql/aggregates/ApproxDistinctAggregate.cpp
index 52ddbf628eaf5..6728a552c3463 100644
--- a/velox/functions/prestosql/aggregates/ApproxDistinctAggregate.cpp
+++ b/velox/functions/prestosql/aggregates/ApproxDistinctAggregate.cpp
@@ -453,19 +453,21 @@ exec::AggregateRegistrationResult registerApproxDistinct(
                              .argumentType("hyperloglog")
                              .build());
   } else {
-    for (const auto& inputType :
-         {"boolean",
-          "tinyint",
-          "smallint",
-          "integer",
-          "bigint",
-          "hugeint",
-          "real",
-          "double",
-          "varchar",
-          "varbinary",
-          "timestamp",
-          "date"}) {
+    for (const auto& inputType : {
+             "boolean",
+             "tinyint",
+             "smallint",
+             "integer",
+             "bigint",
+             "hugeint",
+             "real",
+             "double",
+             "varchar",
+             "varbinary",
+             "timestamp",
+             "date",
+             "unknown",
+         }) {
       signatures.push_back(exec::AggregateFunctionSignatureBuilder()
                                .returnType(returnType)
                                .intermediateType("varbinary")
@@ -505,6 +507,10 @@ exec::AggregateRegistrationResult registerApproxDistinct(
           const TypePtr& resultType,
           const core::QueryConfig& /*config*/)
           -> std::unique_ptr<exec::Aggregate> {
+        if (argTypes[0]->isUnKnown()) {
+          return std::make_unique<ApproxDistinctAggregate<UnknownValue>>(
+              resultType, hllAsFinalResult, hllAsRawInput, defaultError);
+        }
         return VELOX_DYNAMIC_SCALAR_TYPE_DISPATCH(
             createApproxDistinct,
             argTypes[0]->kind(),
diff --git a/velox/functions/prestosql/aggregates/tests/ApproxDistinctTest.cpp b/velox/functions/prestosql/aggregates/tests/ApproxDistinctTest.cpp
index 47c3ac0f8cae4..cb5d3d9bfb783 100644
--- a/velox/functions/prestosql/aggregates/tests/ApproxDistinctTest.cpp
+++ b/velox/functions/prestosql/aggregates/tests/ApproxDistinctTest.cpp
@@ -432,5 +432,44 @@ TEST_F(ApproxDistinctTest, toIntermediate) {
       digests, {"c0"}, {"merge(a0)"}, {"c0", "cardinality(a0)"}, {input});
 }
 
+TEST_F(ApproxDistinctTest, unknownType) {
+  constexpr int kSize = 10;
+  auto input = makeRowVector({
+      makeFlatVector<int32_t>(kSize, [](auto i) { return i % 2; }),
+      makeAllNullFlatVector<UnknownValue>(kSize),
+  });
+  testAggregations(
+      {input},
+      {},
+      {"approx_distinct(c1)", "approx_distinct(c1, 0.023)"},
+      {makeRowVector(std::vector<VectorPtr>(2, makeConstant<int64_t>(0, 1)))});
+  testAggregations(
+      {input},
+      {},
+      {"approx_set(c1)", "approx_set(c1, 0.01625)"},
+      {"cardinality(a0)", "cardinality(a1)"},
+      {makeRowVector(
+          std::vector<VectorPtr>(2, makeNullConstant(TypeKind::BIGINT, 1)))});
+  testAggregations(
+      {input},
+      {"c0"},
+      {"approx_distinct(c1)", "approx_distinct(c1, 0.023)"},
+      {makeRowVector({
+          makeFlatVector<int32_t>({0, 1}),
+          makeFlatVector<int64_t>({0, 0}),
+          makeFlatVector<int64_t>({0, 0}),
+      })});
+  testAggregations(
+      {input},
+      {"c0"},
+      {"approx_set(c1)", "approx_set(c1, 0.01625)"},
+      {"c0", "cardinality(a0)", "cardinality(a1)"},
+      {makeRowVector({
+          makeFlatVector<int32_t>({0, 1}),
+          makeNullConstant(TypeKind::BIGINT, 2),
+          makeNullConstant(TypeKind::BIGINT, 2),
+      })});
+}
+
 } // namespace
 } // namespace facebook::velox::aggregate::test