diff --git a/Kitodo/src/main/java/org/kitodo/production/forms/WorkflowForm.java b/Kitodo/src/main/java/org/kitodo/production/forms/WorkflowForm.java
index 3fdb5ea6c6f..dcc45c1c890 100644
--- a/Kitodo/src/main/java/org/kitodo/production/forms/WorkflowForm.java
+++ b/Kitodo/src/main/java/org/kitodo/production/forms/WorkflowForm.java
@@ -270,8 +270,10 @@ private boolean saveFiles() throws IOException, WorkflowException {
 
         xmlDiagram = requestParameterMap.get("editForm:workflowTabView:xmlDiagram");
         if (Objects.nonNull(xmlDiagram)) {
-            svgDiagram = StringUtils.substringAfter(xmlDiagram, "kitodo-diagram-separator");
-            xmlDiagram = StringUtils.substringBefore(xmlDiagram, "kitodo-diagram-separator");
+            if (xmlDiagram.contains("kitodo-diagram-separator")) {
+                svgDiagram = StringUtils.substringAfter(xmlDiagram, "kitodo-diagram-separator");
+                xmlDiagram = StringUtils.substringBefore(xmlDiagram, "kitodo-diagram-separator");
+            }
 
             Reader reader = new Reader(new ByteArrayInputStream(xmlDiagram.getBytes(StandardCharsets.UTF_8)));
             reader.validateWorkflowTasks();