diff --git a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbItemDocumentExpr.java b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbItemDocumentExpr.java
index 3ecbca5cd..f61b8a8c4 100644
--- a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbItemDocumentExpr.java
+++ b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbItemDocumentExpr.java
@@ -96,12 +96,12 @@ public class WbItemDocumentExpr implements WbExpression<ItemUpdate> {
 
     @JsonProperty("nameDescs")
     public List<WbNameDescExpr> getNameDescs() {
-        return nameDescs;
+        return Collections.unmodifiableList(nameDescs);
     }
 
     @JsonProperty("statementGroups")
     public List<WbStatementGroupExpr> getStatementGroups() {
-        return statementGroups;
+        return Collections.unmodifiableList(statementGroups);
     }
 
     @Override
diff --git a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbReferenceExpr.java b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbReferenceExpr.java
index 7310b0d60..6f1383229 100644
--- a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbReferenceExpr.java
+++ b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbReferenceExpr.java
@@ -24,6 +24,7 @@
 package org.openrefine.wikidata.schema;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.commons.lang.Validate;
@@ -77,7 +78,7 @@ public class WbReferenceExpr implements WbExpression<Reference> {
 
     @JsonProperty("snaks")
     public List<WbSnakExpr> getSnaks() {
-        return snakExprs;
+        return Collections.unmodifiableList(snakExprs);
     }
 
     @Override
diff --git a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementExpr.java b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementExpr.java
index 69e27b326..e57eace9a 100644
--- a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementExpr.java
+++ b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementExpr.java
@@ -134,12 +134,12 @@ public class WbStatementExpr {
 
     @JsonProperty("qualifiers")
     public List<WbSnakExpr> getQualifiers() {
-        return qualifierExprs;
+        return Collections.unmodifiableList(qualifierExprs);
     }
 
     @JsonProperty("references")
     public List<WbReferenceExpr> getReferences() {
-        return referenceExprs;
+        return Collections.unmodifiableList(referenceExprs);
     }
 
     @Override
diff --git a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementGroupExpr.java b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementGroupExpr.java
index 724c8656d..6949439a1 100644
--- a/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementGroupExpr.java
+++ b/extensions/wikidata/src/org/openrefine/wikidata/schema/WbStatementGroupExpr.java
@@ -24,6 +24,7 @@
 package org.openrefine.wikidata.schema;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.jsoup.helper.Validate;
@@ -79,7 +80,7 @@ public class WbStatementGroupExpr {
 
     @JsonProperty("statements")
     public List<WbStatementExpr> getStatements() {
-        return statementExprs;
+        return Collections.unmodifiableList(statementExprs);
     }
 
     @Override
diff --git a/extensions/wikidata/src/org/openrefine/wikidata/schema/WikibaseSchema.java b/extensions/wikidata/src/org/openrefine/wikidata/schema/WikibaseSchema.java
index 413a7dc6b..7230cbef9 100644
--- a/extensions/wikidata/src/org/openrefine/wikidata/schema/WikibaseSchema.java
+++ b/extensions/wikidata/src/org/openrefine/wikidata/schema/WikibaseSchema.java
@@ -25,6 +25,7 @@ package org.openrefine.wikidata.schema;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.openrefine.wikidata.qa.QAWarningStore;
@@ -90,7 +91,7 @@ public class WikibaseSchema implements OverlayModel {
      */
     @JsonIgnore
     public List<WbItemDocumentExpr> getItemDocumentExpressions() {
-        return itemDocumentExprs;
+        return Collections.unmodifiableList(itemDocumentExprs);
     }
     
     public void setItemDocumentExpressions(List<WbItemDocumentExpr> exprs) {
diff --git a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbItemDocumentExprTest.java b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbItemDocumentExprTest.java
index dc8187f13..2b5293a24 100644
--- a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbItemDocumentExprTest.java
+++ b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbItemDocumentExprTest.java
@@ -24,10 +24,12 @@
 package org.openrefine.wikidata.schema;
 
 import java.util.Collections;
+import java.util.List;
 
 import org.openrefine.wikidata.testing.JacksonSerializationTest;
 import org.openrefine.wikidata.updates.ItemUpdate;
 import org.openrefine.wikidata.updates.ItemUpdateBuilder;
+import org.testng.Assert;
 import org.testng.annotations.Test;
 import org.wikidata.wdtk.datamodel.helpers.Datamodel;
 import org.wikidata.wdtk.datamodel.interfaces.ItemIdValue;
@@ -89,4 +91,14 @@ public class WbItemDocumentExprTest extends WbExpressionTest<ItemUpdate> {
     public void testSerialize() {
         JacksonSerializationTest.canonicalSerialization(WbItemDocumentExpr.class, expr, jsonRepresentation);
     }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableNameDescsList() {
+        expr.getNameDescs().clear();
+    }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableStatementGroupsList() {
+        expr.getStatementGroups().clear();
+    }
 }
diff --git a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbReferenceExprTest.java b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbReferenceExprTest.java
index 58cabd3f4..d04e3ae5a 100644
--- a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbReferenceExprTest.java
+++ b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbReferenceExprTest.java
@@ -25,8 +25,10 @@ package org.openrefine.wikidata.schema;
 
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
 
 import org.openrefine.wikidata.testing.JacksonSerializationTest;
+import org.testng.Assert;
 import org.testng.annotations.Test;
 import org.wikidata.wdtk.datamodel.helpers.Datamodel;
 import org.wikidata.wdtk.datamodel.interfaces.Reference;
@@ -77,4 +79,9 @@ public class WbReferenceExprTest extends WbExpressionTest<Reference> {
             throws JsonProcessingException {
         JacksonSerializationTest.canonicalSerialization(WbReferenceExpr.class, expr, jsonRepresentation);
     }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableList() {
+        expr.getSnaks().clear();
+    }
 }
diff --git a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementExprTest.java b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementExprTest.java
index 17ee758b5..51b23b0d6 100644
--- a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementExprTest.java
+++ b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementExprTest.java
@@ -23,11 +23,13 @@
  ******************************************************************************/
 package org.openrefine.wikidata.schema;
 
+import org.testng.Assert;
 import static org.testng.Assert.assertEquals;
 
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.List;
 
 import org.openrefine.wikidata.schema.exceptions.SkipSchemaExpressionException;
 import org.openrefine.wikidata.testing.JacksonSerializationTest;
@@ -155,4 +157,14 @@ public class WbStatementExprTest extends WbExpressionTest<Statement> {
     public void testSerialize() {
         JacksonSerializationTest.canonicalSerialization(WbStatementExpr.class, statementExpr, jsonRepresentation);
     }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableQualifiersList() {
+        statementExpr.getQualifiers().clear();
+    }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableReferencesList() {
+        statementExpr.getReferences().clear();
+    }
 }
diff --git a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementGroupExprTest.java b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementGroupExprTest.java
index 2c568d7f5..e9ad42d1f 100644
--- a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementGroupExprTest.java
+++ b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbStatementGroupExprTest.java
@@ -24,9 +24,11 @@
 package org.openrefine.wikidata.schema;
 
 import java.util.Collections;
+import java.util.List;
 
 import org.openrefine.wikidata.schema.exceptions.SkipSchemaExpressionException;
 import org.openrefine.wikidata.testing.JacksonSerializationTest;
+import org.testng.Assert;
 import org.testng.annotations.Test;
 import org.wikidata.wdtk.datamodel.helpers.Datamodel;
 import org.wikidata.wdtk.datamodel.interfaces.ItemIdValue;
@@ -90,4 +92,9 @@ public class WbStatementGroupExprTest extends WbExpressionTest<StatementGroup> {
             throws JsonProcessingException {
         JacksonSerializationTest.canonicalSerialization(WbStatementGroupExpr.class, expr, jsonRepresentation);
     }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableList() {
+        expr.getStatements().clear();
+    }
 }
diff --git a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WikibaseSchemaTest.java b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WikibaseSchemaTest.java
index 3bae4d83c..ce49c8fd4 100644
--- a/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WikibaseSchemaTest.java
+++ b/extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WikibaseSchemaTest.java
@@ -23,6 +23,7 @@
  ******************************************************************************/
 package org.openrefine.wikidata.schema;
 
+import org.testng.Assert;
 import static org.testng.Assert.assertEquals;
 
 import java.io.IOException;
@@ -157,4 +158,11 @@ public class WikibaseSchemaTest extends WikidataRefineTest {
         expected.add(update1);
         assertEquals(expected, updates);
     }
+
+    @Test(expectedExceptions = UnsupportedOperationException.class)
+    public void testUnmodifiableList() throws IOException {
+        String serialized = TestingData.jsonFromFile("schema/inception.json");
+        WikibaseSchema schema = WikibaseSchema.reconstruct(serialized);
+        schema.getItemDocumentExpressions().clear();
+    }
 }