diff --git a/dhp-workflows/dhp-graph-provision/pom.xml b/dhp-workflows/dhp-graph-provision/pom.xml
index 38b575f3ea..1547056b94 100644
--- a/dhp-workflows/dhp-graph-provision/pom.xml
+++ b/dhp-workflows/dhp-graph-provision/pom.xml
@@ -14,16 +14,6 @@
         <dependency>
             <groupId>org.apache.spark</groupId>
             <artifactId>spark-core_2.11</artifactId>
-            <exclusions>
-                <exclusion>
-                    <groupId>org.slf4j</groupId>
-                    <artifactId>slf4j-api</artifactId>
-                </exclusion>
-                <exclusion>
-                    <groupId>org.slf4j</groupId>
-                    <artifactId>jul-to-slf4j</artifactId>
-                </exclusion>
-            </exclusions>
         </dependency>
         <dependency>
             <groupId>org.apache.spark</groupId>
diff --git a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/SerializableSolrInputDocument.java b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/SerializableSolrInputDocument.java
new file mode 100644
index 0000000000..e8d910e8cd
--- /dev/null
+++ b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/SerializableSolrInputDocument.java
@@ -0,0 +1,19 @@
+package eu.dnetlib.dhp.oa.provision.model;
+
+import org.apache.solr.common.SolrInputDocument;
+import org.apache.solr.common.SolrInputField;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class SerializableSolrInputDocument extends SolrInputDocument {
+
+    public SerializableSolrInputDocument() {
+        super(new HashMap<>());
+    }
+
+    public SerializableSolrInputDocument(Map<String, SolrInputField> fields) {
+        super(fields);
+    }
+
+}