diff --git a/distr/flecs.c b/distr/flecs.c
index bab1cf8f4..2688fd0ba 100644
--- a/distr/flecs.c
+++ b/distr/flecs.c
@@ -31739,6 +31739,7 @@ bool flecs_switch_set(
 
         if (!hdr[0]) {
             hdr[0] = (uint64_t)element;
+            node->next = 0;
         } else {
             ecs_switch_node_t *head = flecs_switch_get_node(sw, (uint32_t)hdr[0]);
             ecs_assert(head->prev == 0, ECS_INTERNAL_ERROR, NULL);
@@ -31746,6 +31747,7 @@ bool flecs_switch_set(
 
             node->next = (uint32_t)hdr[0];
             hdr[0] = (uint64_t)element;
+            ecs_assert(node->next != element, ECS_INTERNAL_ERROR, NULL);
         }
 
         node->prev = 0;
diff --git a/src/datastructures/switch_list.c b/src/datastructures/switch_list.c
index f54fab639..6aa70ac47 100644
--- a/src/datastructures/switch_list.c
+++ b/src/datastructures/switch_list.c
@@ -131,6 +131,7 @@ bool flecs_switch_set(
 
         if (!hdr[0]) {
             hdr[0] = (uint64_t)element;
+            node->next = 0;
         } else {
             ecs_switch_node_t *head = flecs_switch_get_node(sw, (uint32_t)hdr[0]);
             ecs_assert(head->prev == 0, ECS_INTERNAL_ERROR, NULL);
@@ -138,6 +139,7 @@ bool flecs_switch_set(
 
             node->next = (uint32_t)hdr[0];
             hdr[0] = (uint64_t)element;
+            ecs_assert(node->next != element, ECS_INTERNAL_ERROR, NULL);
         }
 
         node->prev = 0;
diff --git a/test/core/project.json b/test/core/project.json
index 21de46d8c..c6fa8a9b0 100644
--- a/test/core/project.json
+++ b/test/core/project.json
@@ -595,7 +595,8 @@
                 "defer_add_union_relationship",
                 "defer_add_existing_union_relationship",
                 "defer_add_union_relationship_2_ops",
-                "defer_add_existing_union_relationship_2_ops"
+                "defer_add_existing_union_relationship_2_ops",
+                "stress_test_1"
             ]
         }, {
             "id": "Hierarchies",
diff --git a/test/core/src/Union.c b/test/core/src/Union.c
index f901be005..c86013bed 100644
--- a/test/core/src/Union.c
+++ b/test/core/src/Union.c
@@ -1444,3 +1444,56 @@ void Union_defer_add_existing_union_relationship_2_ops(void) {
 
     ecs_fini(world);
 }
+
+void Union_stress_test_1(void) {
+    ecs_world_t *world = ecs_mini();
+
+    ECS_ENTITY(world, Rel, Union);
+    ECS_TAG(world, TgtA);
+    ECS_TAG(world, TgtB);
+    ECS_TAG(world, TgtC);
+
+    ecs_entity_t e1 = ecs_new(world);
+    ecs_entity_t e2 = ecs_new(world);
+
+    ecs_add_pair(world, e1, Rel, TgtA);
+    ecs_add_pair(world, e2, Rel, TgtA);
+    ecs_add_pair(world, e2, Rel, TgtB);
+
+    ecs_add_pair(world, e2, Rel, TgtA);
+    ecs_add_pair(world, e2, Rel, TgtB);
+    ecs_add_pair(world, e1, Rel, TgtC);
+
+    ecs_add_pair(world, e1, Rel, TgtA);
+    ecs_add_pair(world, e2, Rel, TgtB);
+    ecs_add_pair(world, e1, Rel, TgtC);
+
+    ecs_add_pair(world, e1, Rel, TgtA);
+    ecs_add_pair(world, e2, Rel, TgtA);
+    ecs_add_pair(world, e1, Rel, TgtC);
+
+    test_assert(ecs_has_pair(world, e1, Rel, TgtC));
+    test_assert(ecs_has_pair(world, e2, Rel, TgtA));
+
+    ecs_query_t *q_tgtA = ecs_query(world, {
+        .terms = {{ ecs_pair(Rel, TgtA) }}
+    });
+
+    ecs_query_t *q_tgtB = ecs_query(world, {
+        .terms = {{ ecs_pair(Rel, TgtB) }}
+    });
+
+    ecs_query_t *q_tgtC = ecs_query(world, {
+        .terms = {{ ecs_pair(Rel, TgtC) }}
+    });
+
+    test_int(ecs_query_count(q_tgtA).entities, 1);
+    test_int(ecs_query_count(q_tgtB).entities, 0);
+    test_int(ecs_query_count(q_tgtC).entities, 1);
+
+    ecs_query_fini(q_tgtA);
+    ecs_query_fini(q_tgtB);
+    ecs_query_fini(q_tgtC);
+
+    ecs_fini(world);
+}
diff --git a/test/core/src/main.c b/test/core/src/main.c
index ecb758b3b..8e72f6e4a 100644
--- a/test/core/src/main.c
+++ b/test/core/src/main.c
@@ -567,6 +567,7 @@ void Union_defer_add_union_relationship(void);
 void Union_defer_add_existing_union_relationship(void);
 void Union_defer_add_union_relationship_2_ops(void);
 void Union_defer_add_existing_union_relationship_2_ops(void);
+void Union_stress_test_1(void);
 
 // Testsuite 'Hierarchies'
 void Hierarchies_setup(void);
@@ -4456,6 +4457,10 @@ bake_test_case Union_testcases[] = {
     {
         "defer_add_existing_union_relationship_2_ops",
         Union_defer_add_existing_union_relationship_2_ops
+    },
+    {
+        "stress_test_1",
+        Union_stress_test_1
     }
 };
 
@@ -11208,7 +11213,7 @@ static bake_test_suite suites[] = {
         "Union",
         NULL,
         NULL,
-        51,
+        52,
         Union_testcases
     },
     {