diff --git a/tests/CTestCustom.cmake b/tests/CTestCustom.cmake
index 4f7cec04c..51cb67445 100644
--- a/tests/CTestCustom.cmake
+++ b/tests/CTestCustom.cmake
@@ -99,4 +99,16 @@ if ((NOT "@FORCE_RUN_ALL_TESTS@" STREQUAL "ON") AND (NOT "@USE_SANITIZER@" STREQ
     )
   endif()
 
+  if("@USE_SANITIZER@" MATCHES "Undefined" AND "@CMAKE_CXX_COMPILER_ID@" STREQUAL "Clang")
+    set(CTEST_CUSTOM_TESTS_IGNORE
+      ${CTEST_CUSTOM_TESTS_IGNORE}
+
+      write_rntuple
+      read_rntuple
+      write_interface_rntuple
+      read_interface_rntuple
+    )
+
+  endif()
+
 endif()
diff --git a/tests/unittests/unittest.cpp b/tests/unittests/unittest.cpp
index 3ce831a12..5f110ded8 100644
--- a/tests/unittests/unittest.cpp
+++ b/tests/unittests/unittest.cpp
@@ -1380,16 +1380,16 @@ TEST_CASE("ROOTWriter check consistency", "[ASAN-FAIL][UBSAN-FAIL][basics][root]
 
 #if PODIO_ENABLE_RNTUPLE
 
-TEST_CASE("Relations after cloning with RNTuple", "[THREAD-FAIL][relations][basics]") {
+TEST_CASE("Relations after cloning with RNTuple", "[THREAD-FAIL][UBSAN-FAIL][relations][basics]") {
   runRelationAfterCloneCheck<podio::RNTupleReader, podio::RNTupleWriter>(
       "unittests_relations_after_cloning_rntuple.root");
 }
 
-TEST_CASE("RNTupleWriter consistent frame contents", "[basics][root]") {
+TEST_CASE("RNTupleWriter consistent frame contents", "[UBSAN-FAIL][basics][root]") {
   runConsistentFrameTest<podio::RNTupleWriter>("unittests_frame_consistency_rntuple.root");
 }
 
-TEST_CASE("RNTupleWriter check consistency", "[basics][root]") {
+TEST_CASE("RNTupleWriter check consistency", "[UBSAN-FAIL][basics][root]") {
   runCheckConsistencyTest<podio::RNTupleWriter>("unittests_frame_check_consistency_rntuple.root");
 }