diff --git a/test-cases/RMLTC0013a-MySQL/mapping.ttl b/test-cases/RMLTC0013a-MySQL/mapping.ttl
index e31950d..85cae74 100644
--- a/test-cases/RMLTC0013a-MySQL/mapping.ttl
+++ b/test-cases/RMLTC0013a-MySQL/mapping.ttl
@@ -23,7 +23,7 @@
   rr:predicateObjectMap [ 
     rr:predicate ex:BirthDay ; 
     rr:objectMap [
-      rr:reference "DateOfBirth";
+      rml:reference "DateOfBirth";
     ]
   ];
   .
diff --git a/test-cases/RMLTC0013a-PostgreSQL/mapping.ttl b/test-cases/RMLTC0013a-PostgreSQL/mapping.ttl
index f0cba80..831b9e1 100644
--- a/test-cases/RMLTC0013a-PostgreSQL/mapping.ttl
+++ b/test-cases/RMLTC0013a-PostgreSQL/mapping.ttl
@@ -23,7 +23,7 @@
   rr:predicateObjectMap [ 
     rr:predicate ex:BirthDay ; 
     rr:objectMap [
-      rr:reference "DateOfBirth";
+      rml:reference "DateOfBirth";
     ]
   ];
   .
diff --git a/test-cases/RMLTC0013a-SQLServer/mapping.ttl b/test-cases/RMLTC0013a-SQLServer/mapping.ttl
index f7a69fb..eff3e72 100644
--- a/test-cases/RMLTC0013a-SQLServer/mapping.ttl
+++ b/test-cases/RMLTC0013a-SQLServer/mapping.ttl
@@ -23,7 +23,7 @@
   rr:predicateObjectMap [ 
     rr:predicate ex:BirthDay ; 
     rr:objectMap [
-      rr:reference "DateOfBirth";
+      rml:reference "DateOfBirth";
     ]
   ];
   .