diff --git a/src/AggregateFunctions/AggregateFunctionNull.cpp b/src/AggregateFunctions/AggregateFunctionNull.cpp
index 77687f9f328..993cb93c991 100644
--- a/src/AggregateFunctions/AggregateFunctionNull.cpp
+++ b/src/AggregateFunctions/AggregateFunctionNull.cpp
@@ -33,6 +33,11 @@ public:
     AggregateFunctionPtr transformAggregateFunction(
         const AggregateFunctionPtr & nested_function, const DataTypes & arguments, const Array & params) const override
     {
+        /// Special case for 'count' function. It could be called with Nullable arguments
+        /// - that means - count number of calls, when all arguments are not NULL.
+        if (nested_function && nested_function->getName() == "count")
+            return std::make_shared<AggregateFunctionCountNotNullUnary>(arguments[0], params);
+
         bool has_nullable_types = false;
         bool has_null_types = false;
         for (const auto & arg_type : arguments)
@@ -60,11 +65,6 @@ public:
         if (auto adapter = nested_function->getOwnNullAdapter(nested_function, arguments, params))
             return adapter;
 
-        /// Special case for 'count' function. It could be called with Nullable arguments
-        /// - that means - count number of calls, when all arguments are not NULL.
-        if (nested_function->getName() == "count")
-            return std::make_shared<AggregateFunctionCountNotNullUnary>(arguments[0], params);
-
         bool return_type_is_nullable = !nested_function->returnDefaultWhenOnlyNull() && nested_function->getReturnType()->canBeInsideNullable();
         bool serialize_flag = return_type_is_nullable || nested_function->returnDefaultWhenOnlyNull();
 
diff --git a/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.reference b/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.reference
new file mode 100644
index 00000000000..f8b77704aa3
--- /dev/null
+++ b/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.reference
@@ -0,0 +1,9 @@
+0
+0
+0
+5
+5
+5
+0
+\N
+\N
diff --git a/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.sql b/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.sql
new file mode 100644
index 00000000000..2d9b5ef54aa
--- /dev/null
+++ b/tests/queries/0_stateless/01315_count_distinct_return_not_nullable.sql
@@ -0,0 +1,12 @@
+SELECT uniq(number >= 10 ? number : NULL) FROM numbers(10);
+SELECT uniqExact(number >= 10 ? number : NULL) FROM numbers(10);
+SELECT count(DISTINCT number >= 10 ? number : NULL) FROM numbers(10);
+
+SELECT uniq(number >= 5 ? number : NULL) FROM numbers(10);
+SELECT uniqExact(number >= 5 ? number : NULL) FROM numbers(10);
+SELECT count(DISTINCT number >= 5 ? number : NULL) FROM numbers(10);
+
+SELECT count(NULL);
+-- These two returns NULL for now, but we want to change them to return 0.
+SELECT uniq(NULL);
+SELECT count(DISTINCT NULL);