diff --git a/rel2graph/core/converter.py b/rel2graph/core/converter.py
index 518d3b2..3dd9bd3 100644
--- a/rel2graph/core/converter.py
+++ b/rel2graph/core/converter.py
@@ -103,13 +103,20 @@ def commit_batch(to_create: Subgraph, to_merge: Subgraph) -> None:
         nodes_committed = 0 
         relationships_committed = 0
         
-        # Creating does not rely on synchronous executions
-        if len(to_create.nodes) + len(to_create.relationships) > 0:
+        # Creating nodes does not rely on serialized executions
+        # If there are relationships to create, we need to serialize the creation
+        # TODO: We could split the creation of nodes and relationships into two separate branches, might be more efficient
+        #       but considering that in almost all cases no relationships are created in the first loop, it's not worth it
+        if len(to_create.relationships) > 0:
+            with __process_config.graph_lock:
+                with __process_config.graph_driver.session() as session:
+                    commit_wrap(lambda: create(to_create, session))
+            relationships_committed += len(to_create.relationships)
+        elif len(to_create.nodes) > 0:
             with __process_config.graph_driver.session() as session:
                 commit_wrap(lambda: create(to_create, session))
             nodes_committed += len(to_create.nodes)
-            relationships_committed += len(to_create.relationships)
-            
+
         # Merging nodes requires serialization (synchronous executions) between processes
         # Using locks to enforce this
         if len(to_merge.nodes) + len(to_merge.relationships) > 0:
diff --git a/rel2graph/neo4j/__init__.py b/rel2graph/neo4j/__init__.py
index 9c485f4..8f703ec 100644
--- a/rel2graph/neo4j/__init__.py
+++ b/rel2graph/neo4j/__init__.py
@@ -45,7 +45,7 @@ def pull(graph: Subgraph, session: Session):
         graph (Subgraph): The graph to create.
         session (Session): The `session <https://neo4j.com/docs/api/python-driver/current/api.html#session>`_ to use.
     """
-    session.execute_write(graph.__db_pull__)
+    session.execute_read(graph.__db_pull__)
 
 
 def match_nodes(session: Session, *labels: List[str], **properties: dict):
diff --git a/tests/integration/resources/schema_concurrency.yaml b/tests/integration/resources/schema_concurrency.yaml
new file mode 100644
index 0000000..855a03e
--- /dev/null
+++ b/tests/integration/resources/schema_concurrency.yaml
@@ -0,0 +1,8 @@
+ENTITY("Entity"):
+  NODE("Test"):
+    + uid = Entity.uid
+
+
+ENTITY("Relationship"):
+  RELATIONSHIP(MATCH("Test", uid=Relationship.to), "FROM", MATCH("Test", uid=Relationship.from)):
+  MERGE_RELATIONSHIPS(RELATIONSHIP(MATCH("Test", uid=Relationship.from), "TO", MATCH("Test", uid=Relationship.to))):
diff --git a/tests/integration/test_concurrency.py b/tests/integration/test_concurrency.py
new file mode 100644
index 0000000..8e8125b
--- /dev/null
+++ b/tests/integration/test_concurrency.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Integration tests for testing the synchronous conversion of relations. Related to issue #20.
+
+authors: Julian Minder
+"""
+
+import pytest 
+
+import pandas as pd
+import logging
+import numpy as np
+
+from rel2graph import Converter, IteratorIterator, register_attribute_postprocessor, Attribute, register_subgraph_preprocessor, GlobalSharedState, register_subgraph_postprocessor
+from rel2graph.utils import load_file
+from rel2graph.relational_modules.pandas import PandasDataFrameIterator
+from rel2graph.neo4j import match_relationships, push, pull
+from rel2graph.common_modules import MERGE_RELATIONSHIPS
+
+from helpers import *
+
+
+# As this issue is related to multiple workers, we repeat the test multiple times
+@pytest.mark.parametrize('execution_number', range(10))
+def test_concurrent_relationships(execution_number, session, uri, auth):
+    schema = load_file("tests/integration/resources/schema_concurrency.yaml")
+
+    entities = pd.DataFrame({"uid": range(40)})
+
+    # 120 relations between 20 entities
+    relations = pd.DataFrame({"from": list(range(20))*6, "to": [i+20 for i in range(20) for _ in range(6)]})
+    unique_pairs = len(relations.drop_duplicates())
+    print(unique_pairs)
+
+    iterator = IteratorIterator([PandasDataFrameIterator(entities, "Entity"), PandasDataFrameIterator(relations, "Relationship")])
+
+    converter = Converter(schema, iterator, uri, auth, num_workers=12, batch_size=10)
+    converter(skip_relationships=False)
+
+
+    assert num_relationships(session) == 120+unique_pairs
+    assert num_nodes(session) == 40
\ No newline at end of file
diff --git a/tests/integration/test_merge.py b/tests/integration/test_merge.py
index 1ec4f10..056004a 100644
--- a/tests/integration/test_merge.py
+++ b/tests/integration/test_merge.py
@@ -58,7 +58,7 @@ def test_standart_same_resource(config, session, uri, auth):
 
 
 @pytest.mark.parametrize("config",[(1,True), (1, False) ,(5, False)])
-def test_merge_nodesasdf(config, session, uri, auth):
+def test_merge_nodes(config, session, uri, auth):
     schema = """
     ENTITY("Entity"):
         NODE("Entity") node: