diff --git a/modules/nextflow/src/main/groovy/nextflow/util/ArrayBag.groovy b/modules/nextflow/src/main/groovy/nextflow/util/ArrayBag.groovy
index 64e849085c..bd7dcff3b8 100644
--- a/modules/nextflow/src/main/groovy/nextflow/util/ArrayBag.groovy
+++ b/modules/nextflow/src/main/groovy/nextflow/util/ArrayBag.groovy
@@ -63,53 +63,66 @@ class ArrayBag<E> implements Bag<E>, List<E>, KryoSerializable {
         InvokerHelper.inspect(this)
     }
 
-//    E getAt( int index )  {
-//        target.get(index)
-//    }
-//
-//    void putAt( int index, E value ) {
-//        target.set(index, value)
-//    }
-//
-//    @Override
-//    int hashCode() {
-//        int h = 0;
-//        Iterator<E> i = target.iterator();
-//        while (i.hasNext()) {
-//            E obj = i.next();
-//            if (obj != null)
-//                h += obj.hashCode();
-//        }
-//        return h;
-//    }
-//
-//    @Override
-//    boolean equals(Object o) {
-//        if ( o.is(this) )
-//            return true;
-//
-//        if (!(o instanceof ArrayBag))
-//            return false;
-//
-//        Collection other = ((ArrayBag)o).target
-//        if (other.size() != target.size())
-//            return false;
-//
-//        try {
-//            return target.containsAll(other);
-//        }
-//        catch (ClassCastException unused)   {
-//            return false;
-//        }
-//        catch (NullPointerException unused) {
-//            return false;
-//        }
-//    }
+    @Override
+    int hashCode() {
+        int h = 0;
+        Iterator<E> i = target.iterator();
+        while (i.hasNext()) {
+            E obj = i.next();
+            if (obj != null)
+                h += obj.hashCode();
+        }
+        return h;
+    }
+
+    /**
+     * NOTE!!! this method implements an equality is NOT used when invoking `equals` method
+     * or using `==` operator from Groovy code. This because the Groovy runtime implements its
+     * own equality logic both for {@link Map} and {@link Collection} logic.
+     *
+     * See
+     * https://issues.apache.org/jira/browse/GROOVY-9003
+     *
+     * However this is still applied when equality is checked by Java compiled code e.g. Java SDK.
+     * For this reason is necessary to implement the expected equals (and hashCode) semantic by `join`
+     * (and other) operators.
+     *
+     * See issue
+     * https://github.com/nextflow-io/nextflow/issues/5187
+     *
+     * @return
+     *      {@code true} is the content of the bag is equals to another bag irrespective the elements order,
+     *      {@code false} otherwise
+     */
+    @Override
+    boolean equals(Object o) {
+        if ( o.is(this) )
+            return true;
+
+        if (!(o instanceof ArrayBag))
+            return false;
 
+        Collection other = ((ArrayBag)o).target
+        if (other.size() != target.size())
+            return false;
+
+        try {
+            return target.containsAll(other);
+        }
+        catch (ClassCastException unused)   {
+            return false;
+        }
+        catch (NullPointerException unused) {
+            return false;
+        }
+    }
+
+    @Override
     void read (Kryo kryo, Input input) {
         target = kryo.readObject(input,ArrayList)
     }
 
+    @Override
     void write (Kryo kryo, Output output) {
         kryo.writeObject(output, target)
     }
diff --git a/modules/nextflow/src/test/groovy/nextflow/extension/JoinOpTest.groovy b/modules/nextflow/src/test/groovy/nextflow/extension/JoinOpTest.groovy
index 9893d9a797..673686fdf9 100644
--- a/modules/nextflow/src/test/groovy/nextflow/extension/JoinOpTest.groovy
+++ b/modules/nextflow/src/test/groovy/nextflow/extension/JoinOpTest.groovy
@@ -21,7 +21,9 @@ import nextflow.Channel
 import nextflow.Global
 import nextflow.Session
 import nextflow.exception.AbortOperationException
+import nextflow.util.ArrayBag
 import spock.lang.Specification
+
 /**
  *
  * @author Paolo Di Tommaso <paolo.ditommaso@gmail.com>
@@ -207,6 +209,35 @@ class JoinOpTest extends Specification {
 
     }
 
+    def 'should be able to use identical ArrayBags join key' () {
+        given:
+        def key1 = new ArrayBag(["key"])
+        def key2 = new ArrayBag(["key"])
+        def ch1 = Channel.of([key1, "foo"])
+        def ch2 = Channel.of([key2, "bar"])
+
+        when:
+        def op = new JoinOp(ch1 as DataflowReadChannel, ch2 as DataflowReadChannel)
+        List result = op.apply().toList().getVal()
+
+        then:
+        !result.isEmpty()
+    }
+
+    def 'should differentiate nonidentical ArrayBags join key' () {
+        given:
+        def key1 = new ArrayBag(["key", "key", "quay"])
+        def key2 = new ArrayBag(["quay", "quay", "key"])
+        def ch1 = Channel.of([key1, "foo"])
+        def ch2 = Channel.of([key2, "bar"])
+
+        when:
+        def op = new JoinOp(ch1 as DataflowReadChannel, ch2 as DataflowReadChannel)
+        List result = op.apply().toList().getVal()
+
+        then:
+        result.isEmpty()
+    }
 
     def 'should not fail on mismatches' () {
         given:
diff --git a/modules/nextflow/src/test/groovy/nextflow/util/ArrayBagTest.groovy b/modules/nextflow/src/test/groovy/nextflow/util/ArrayBagTest.groovy
index 0eb91521a6..b4e0b8efb4 100644
--- a/modules/nextflow/src/test/groovy/nextflow/util/ArrayBagTest.groovy
+++ b/modules/nextflow/src/test/groovy/nextflow/util/ArrayBagTest.groovy
@@ -74,4 +74,35 @@ class ArrayBagTest extends Specification {
         String.valueOf(bag) == '[1, 2, 3]'
     }
 
+    def 'hashCode should be invariant to order' () {
+        given:
+        def bag1 = new ArrayBag([1,2,3])
+        def bag2 = new ArrayBag([3,1,2])
+        def bag3 = new ArrayBag([4,1,2])
+
+        expect:
+        bag1.hashCode() == bag2.hashCode()
+        bag1.hashCode() != bag3.hashCode()
+
+        /**
+         * NOTE!!! equality cannot be checked due to groovy overriding the equals implementation
+         * see {@link ArrayBag#equals(java.lang.Object)}
+         */
+    }
+
+    def 'should access map entry using bag as key' () {
+        given:
+        def bag1 = new ArrayBag([1,2,3])
+        def bag2 = new ArrayBag([3,1,2])
+        def bag3 = new ArrayBag([4,1,2])
+        and:
+        def map = [(bag1):'foo']
+
+        expect:
+        map.get(bag1) == 'foo'
+        map.get(bag2) == 'foo'
+        map.get(bag3) == null
+
+    }
+
 }