diff --git a/opencga-storage/opencga-storage-core/src/main/java/org/opencb/opencga/storage/core/variant/VariantStorageEngine.java b/opencga-storage/opencga-storage-core/src/main/java/org/opencb/opencga/storage/core/variant/VariantStorageEngine.java
index 81ddc4c0e3..e559592aa2 100644
--- a/opencga-storage/opencga-storage-core/src/main/java/org/opencb/opencga/storage/core/variant/VariantStorageEngine.java
+++ b/opencga-storage/opencga-storage-core/src/main/java/org/opencb/opencga/storage/core/variant/VariantStorageEngine.java
@@ -326,9 +326,11 @@ public List<URI> walkData(URI outputFile, VariantWriterFactory.VariantOutputForm
     }
 
 
-    public abstract List<URI> walkData(URI outputFile, VariantOutputFormat format, Query query, QueryOptions queryOptions,
+    public List<URI> walkData(URI outputFile, VariantOutputFormat format, Query query, QueryOptions queryOptions,
                                        String commandLine)
-            throws StorageEngineException;
+            throws StorageEngineException {
+        throw new UnsupportedOperationException();
+    }
 
     /**
      * Creates a new {@link VariantExporter} for the current backend.