diff --git a/src/Processors/QueryPlan/DistinctStep.cpp b/src/Processors/QueryPlan/DistinctStep.cpp
index 0628048411a..60966b08beb 100644
--- a/src/Processors/QueryPlan/DistinctStep.cpp
+++ b/src/Processors/QueryPlan/DistinctStep.cpp
@@ -8,16 +8,16 @@ namespace DB
 
 static bool checkColumnsAlreadyDistinct(const Names & columns, const NameSet & distinct_names)
 {
-    bool columns_already_distinct = true;
-    if (columns.size() != distinct_names.size()) {
-        columns_already_distinct = false;
-    } else {
-        for (const auto & name : columns)
-            if (distinct_names.count(name) == 0)
-                columns_already_distinct = false;
-    }
+    if (distinct_names.empty())
+        return false;
 
-    return columns_already_distinct;
+    /// Now we need to check that distinct_names is a subset of columns.
+    std::unordered_set<std::string_view> columns_set(columns.begin(), columns.end());
+    for (const auto & name : distinct_names)
+        if (columns_set.count(name) == 0)
+            return false;
+
+    return true;
 }
 
 static ITransformingStep::Traits getTraits(bool pre_distinct, bool already_distinct_columns)