diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericCollection.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericCollection.java
index f9a5f96ac..6e362a89a 100644
--- a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericCollection.java
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericCollection.java
@@ -13,6 +13,8 @@
  */
 package com.querydsl.core.group;
 
+import static com.querydsl.core.util.TupleUtils.toTuple;
+
 import com.querydsl.core.FetchableQuery;
 import com.querydsl.core.Tuple;
 import com.querydsl.core.types.Expression;
@@ -53,29 +55,30 @@ public RES transform(FetchableQuery<?, ?> query) {
     if (hasGroups) {
       expr = withoutGroupExpressions(expr);
     }
-    final var iter = query.select(expr).iterate();
+    try (final var iter = query.select(expr).iterate(); ) {
 
-    var list = resultFactory.get();
-    GroupImpl group = null;
-    K groupId = null;
-    while (iter.hasNext()) {
-      @SuppressWarnings("unchecked") // This type is mandated by the key type
-      var row = (K[]) iter.next().toArray();
-      if (group == null) {
-        group = new GroupImpl(groupExpressions, maps);
-        groupId = row[0];
-      } else if (!Objects.equals(groupId, row[0])) {
+      var list = resultFactory.get();
+      GroupImpl group = null;
+      K groupId = null;
+      while (iter.hasNext()) {
+        var tuple = toTuple(iter.next(), expressions);
+        @SuppressWarnings("unchecked") // This type is mandated by the key type
+        var row = (K[]) tuple.toArray();
+        if (group == null) {
+          group = new GroupImpl(groupExpressions, maps);
+          groupId = row[0];
+        } else if (!Objects.equals(groupId, row[0])) {
+          list.add(transform(group));
+          group = new GroupImpl(groupExpressions, maps);
+          groupId = row[0];
+        }
+        group.add(row);
+      }
+      if (group != null) {
         list.add(transform(group));
-        group = new GroupImpl(groupExpressions, maps);
-        groupId = row[0];
       }
-      group.add(row);
-    }
-    if (group != null) {
-      list.add(transform(group));
+      return list;
     }
-    iter.close();
-    return list;
   }
 
   @SuppressWarnings("unchecked")
diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericMap.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericMap.java
index 0418a0b32..eeed50baa 100644
--- a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericMap.java
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericMap.java
@@ -13,6 +13,8 @@
  */
 package com.querydsl.core.group;
 
+import static com.querydsl.core.util.TupleUtils.toTuple;
+
 import com.querydsl.core.FetchableQuery;
 import com.querydsl.core.Tuple;
 import com.querydsl.core.types.Expression;
@@ -53,11 +55,11 @@ public RES transform(FetchableQuery<?, ?> query) {
     if (hasGroups) {
       expr = withoutGroupExpressions(expr);
     }
-    var iter = query.select(expr).iterate();
-    try {
+    try (var iter = query.select(expr).iterate()) {
       while (iter.hasNext()) {
+        var tuple = toTuple(iter.next(), expressions);
         @SuppressWarnings("unchecked") // This type is mandated by the key type
-        var row = (K[]) iter.next().toArray();
+        var row = (K[]) tuple.toArray();
         var groupId = row[0];
         var group = (GroupImpl) groups.get(groupId);
         if (group == null) {
@@ -66,8 +68,6 @@ public RES transform(FetchableQuery<?, ?> query) {
         }
         group.add(row);
       }
-    } finally {
-      iter.close();
     }
 
     // transform groups
diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByIterate.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByIterate.java
index 02e78b54d..d7f0d8899 100644
--- a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByIterate.java
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByIterate.java
@@ -13,6 +13,8 @@
  */
 package com.querydsl.core.group;
 
+import static com.querydsl.core.util.TupleUtils.toTuple;
+
 import com.mysema.commons.lang.CloseableIterator;
 import com.querydsl.core.FetchableQuery;
 import com.querydsl.core.Tuple;
@@ -73,8 +75,9 @@ public V next() {
         }
 
         while (iter.hasNext()) {
+          var tuple = toTuple(iter.next(), expressions);
           @SuppressWarnings("unchecked") // This type is mandated by the key type
-          var row = (K[]) iter.next().toArray();
+          var row = (K[]) tuple.toArray();
           if (group == null) {
             group = new GroupImpl(groupExpressions, maps);
             groupId = row[0];
diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByMap.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByMap.java
index eb50a0e41..b9527dc13 100644
--- a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByMap.java
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/group/GroupByMap.java
@@ -13,6 +13,8 @@
  */
 package com.querydsl.core.group;
 
+import static com.querydsl.core.util.TupleUtils.toTuple;
+
 import com.querydsl.core.FetchableQuery;
 import com.querydsl.core.Tuple;
 import com.querydsl.core.types.Expression;
@@ -50,8 +52,9 @@ public Map<K, V> transform(FetchableQuery<?, ?> query) {
     }
     try (var iter = query.select(expr).iterate()) {
       while (iter.hasNext()) {
+        var tuple = toTuple(iter.next(), expressions);
         @SuppressWarnings("unchecked") // This type is mandated by the key type
-        var row = (K[]) iter.next().toArray();
+        var row = (K[]) tuple.toArray();
         var groupId = row[0];
         var group = (GroupImpl) groups.get(groupId);
         if (group == null) {
diff --git a/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/util/TupleUtils.java b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/util/TupleUtils.java
new file mode 100644
index 000000000..86ef005d2
--- /dev/null
+++ b/querydsl-libraries/querydsl-core/src/main/java/com/querydsl/core/util/TupleUtils.java
@@ -0,0 +1,22 @@
+package com.querydsl.core.util;
+
+import com.querydsl.core.Tuple;
+import com.querydsl.core.types.Expression;
+import com.querydsl.core.types.Projections;
+
+/** TupleUtils provides tuple related utility functionality */
+public final class TupleUtils {
+
+  public static Tuple toTuple(Object next, Expression<?>[] expressions) {
+    // workaround from https://github.com/querydsl/querydsl/issues/3264
+    Tuple tuple;
+    if (next instanceof Tuple) {
+      tuple = (Tuple) next;
+    } else if (next instanceof Object[]) {
+      tuple = Projections.tuple(expressions).newInstance((Object[]) next);
+    } else {
+      throw new IllegalArgumentException(String.format("Could not translate %s into tuple", next));
+    }
+    return tuple;
+  }
+}
diff --git a/querydsl-libraries/querydsl-jpa/src/test/java/com/querydsl/jpa/HibernateBase.java b/querydsl-libraries/querydsl-jpa/src/test/java/com/querydsl/jpa/HibernateBase.java
index 698c8652b..4b2871944 100644
--- a/querydsl-libraries/querydsl-jpa/src/test/java/com/querydsl/jpa/HibernateBase.java
+++ b/querydsl-libraries/querydsl-jpa/src/test/java/com/querydsl/jpa/HibernateBase.java
@@ -14,10 +14,14 @@
 package com.querydsl.jpa;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 import com.mysema.commons.lang.CloseableIterator;
 import com.querydsl.core.DefaultQueryMetadata;
+import com.querydsl.core.Target;
 import com.querydsl.core.Tuple;
+import com.querydsl.core.group.GroupBy;
+import com.querydsl.core.testutil.ExcludeIn;
 import com.querydsl.core.types.EntityPath;
 import com.querydsl.core.types.Expression;
 import com.querydsl.jpa.domain.Cat;
@@ -159,4 +163,17 @@ public void createQuery3() {
       assertThat(row instanceof String).isTrue();
     }
   }
+
+  @Test
+  @ExcludeIn(Target.DERBY)
+  public void createQuery4() {
+    assertDoesNotThrow(
+        () ->
+            query()
+                .from(cat)
+                .leftJoin(cat.kittens)
+                .fetchJoin()
+                .distinct()
+                .transform(GroupBy.groupBy(cat.id).as(cat)));
+  }
 }