diff --git a/.gitignore b/.gitignore
index 8da0b83df..ffa686f7f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@ install
 tests/src
 tests/datamodel
 tests/extension_model
+tests/interface_extension_model
 tests/datamodeljulia
 tests/unittests/Project.toml
 tests/unittests/Manifest.toml
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 65608cca7..c2815738e 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -48,6 +48,21 @@ PODIO_ADD_ROOT_IO_DICT(ExtensionDataModelDict ExtensionDataModel "${ext_headers}
 
 PODIO_ADD_SIO_IO_BLOCKS(ExtensionDataModel "${ext_headers}" "${ext_sources}")
 
+# Build the interface extension data model and link it against the upstream model
+PODIO_GENERATE_DATAMODEL(interface_extension_model datalayout_interface_extension.yaml iext_headers iext_sources
+  UPSTREAM_EDM datamodel:datalayout.yaml
+  IO_BACKEND_HANDLERS ${PODIO_IO_HANDLERS}
+  OUTPUT_FOLDER ${CMAKE_CURRENT_SOURCE_DIR}/interface_extension_model)
+
+PODIO_ADD_DATAMODEL_CORE_LIB(InterfaceExtensionDataModel "${iext_headers}" "${iext_sources}"
+  OUTPUT_FOLDER ${CMAKE_CURRENT_SOURCE_DIR}/interface_extension_model)
+target_link_libraries(InterfaceExtensionDataModel PUBLIC TestDataModel)
+
+PODIO_ADD_ROOT_IO_DICT(InterfaceExtensionDataModelDict InterfaceExtensionDataModel "${iext_headers}" ${CMAKE_CURRENT_SOURCE_DIR}/interface_extension_model/src/selection.xml
+  OUTPUT_FOLDER ${CMAKE_CURRENT_SOURCE_DIR}/interface_extension_model)
+
+PODIO_ADD_SIO_IO_BLOCKS(InterfaceExtensionDataModel "${iext_headers}" "${iext_sources}")
+
 # Add a legacy test case based on a base executable and a version for which an
 # input file exists
 macro(ADD_PODIO_LEGACY_TEST version base_test input_file)
diff --git a/tests/datalayout_interface_extension.yaml b/tests/datalayout_interface_extension.yaml
new file mode 100644
index 000000000..a873d6cde
--- /dev/null
+++ b/tests/datalayout_interface_extension.yaml
@@ -0,0 +1,35 @@
+---
+schema_version: 1
+options:
+  getSyntax: False
+  exposePODMembers: False
+  includeSubfolder: True
+
+components:
+  iextension::PolarVector:
+    Members:
+      - float r
+      - float theta
+      - float phi
+
+datatypes:
+  iextension::AnotherHit:
+    Author: "Mateusz Jakub Fila"
+    Description: "A datatype in the extension with components from the extension and an upstream datamodel"
+    Members:
+     - unsigned long long cellID       // cellID
+     - SimpleStruct aStruct            // component defined in an upstream datamodel
+     - iextension::PolarVector aVector // component defined in the extension
+     - double energy [GeV]             // measured energy deposit
+
+interfaces:
+  iextension::EnergyInterface:
+    Description: "Generic interface for types with an energy member"
+    Author: "Mateusz Jakub Fila"
+    Types:
+      - ExampleHit
+      - ExampleMC
+      - ExampleCluster
+      - iextension::AnotherHit
+    Members:
+      - double energy // the energy
diff --git a/tests/unittests/CMakeLists.txt b/tests/unittests/CMakeLists.txt
index 07c304a57..10f67f66a 100644
--- a/tests/unittests/CMakeLists.txt
+++ b/tests/unittests/CMakeLists.txt
@@ -41,7 +41,7 @@ endif()
 
 find_package(Threads REQUIRED)
 add_executable(unittest_podio unittest.cpp frame.cpp buffer_factory.cpp interface_types.cpp std_interoperability.cpp links.cpp)
-target_link_libraries(unittest_podio PUBLIC TestDataModel PRIVATE Catch2::Catch2WithMain Threads::Threads podio::podioRootIO)
+target_link_libraries(unittest_podio PUBLIC TestDataModel InterfaceExtensionDataModel PRIVATE Catch2::Catch2WithMain Threads::Threads podio::podioRootIO)
 if (ENABLE_SIO)
   target_link_libraries(unittest_podio PRIVATE podio::podioSioIO)
 endif()
diff --git a/tests/unittests/interface_types.cpp b/tests/unittests/interface_types.cpp
index 876e7c14e..b8d649aa6 100644
--- a/tests/unittests/interface_types.cpp
+++ b/tests/unittests/interface_types.cpp
@@ -6,6 +6,10 @@
 #include "datamodel/MutableExampleMC.h"
 #include "datamodel/TypeWithEnergy.h"
 
+#include "interface_extension_model/AnotherHit.h"
+#include "interface_extension_model/EnergyInterface.h"
+#include "interface_extension_model/MutableAnotherHit.h"
+
 #include "podio/ObjectID.h"
 #include "podio/utilities/TypeHelpers.h"
 
@@ -131,3 +135,26 @@ TEST_CASE("InterfaceType getters", "[basics][interface-types][code-gen]") {
   TypeWithEnergy interfaceType = cluster;
   REQUIRE(interfaceType.energy() == 3.14f);
 }
+
+TEST_CASE("InterfaceType extension model", "[interface-types][extension]") {
+  using WrapperT = iextension::EnergyInterface;
+
+  auto wrapper = WrapperT::makeEmpty();
+  REQUIRE_FALSE(wrapper.isAvailable());
+
+  MutableExampleCluster cluster{};
+  cluster.energy(3.14f);
+  wrapper = cluster;
+
+  REQUIRE(wrapper.energy() == 3.14f);
+  REQUIRE(wrapper.isA<ExampleCluster>());
+  REQUIRE(wrapper.as<ExampleCluster>().energy() == 3.14f);
+
+  iextension::MutableAnotherHit hit{};
+  hit.energy(4.2f);
+  wrapper = hit;
+
+  REQUIRE(wrapper.energy() == 4.2f);
+  REQUIRE(wrapper.isA<iextension::AnotherHit>());
+  REQUIRE(wrapper.as<iextension::AnotherHit>().energy() == 4.2f);
+}