diff --git a/Applications/CLI/CMakeLists.txt b/Applications/CLI/CMakeLists.txt
index c1f3e9d361b8f6c469825abffa03e9fee0be7108..b71b45707f08fb5dc7f55050018f321f092ec839 100644
--- a/Applications/CLI/CMakeLists.txt
+++ b/Applications/CLI/CMakeLists.txt
@@ -7,15 +7,12 @@ target_link_libraries(ogs
     ApplicationsLib
     BaseLib
     FileIO
+    InSituLib
     MeshLib
     ${Boost_LIBRARIES}
+    ${CATALYST_LIBRARIES}
+
 )
-if(NOT OGS_DONT_USE_VTK)
-    target_link_libraries(ogs
-        InSituLib
-        ${CATALYST_LIBRARIES}
-    )
-endif()
 
 ADD_CATALYST_DEPENDENCY(ogs)
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4d3511652381d73fcc579fd948be7cb1e3b4f013..7fd4695a645dc2b20fa0c624c8b05509d174389d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,10 +48,6 @@ endif() # GCC AND GPROF_PATH
 
 # Enable / Disable parts
 option(OGS_DONT_USE_QT "Disables all Qt specific code." OFF)
-option(OGS_DONT_USE_VTK "Disables all VTK specific code." OFF)
-if(OGS_DONT_USE_VTK)
-	add_definitions(-DOGS_DONT_USE_VTK)
-endif()
 
 option(OGS_BUILD_CLI "Should the OGS simulator be built?" ON)
 option(OGS_BUILD_TESTS "Should the test executables be built?" ON)
@@ -100,9 +96,7 @@ include(scripts/cmake/packaging/Pack.cmake)
 option(Boost_USE_STATIC_LIBS "This option has to be set from the command line (before boost gets found)!" OFF)
 include(scripts/cmake/ExternalProjectBoost.cmake)
 option(OGS_SYSTEM_VTK_ONLY "If On VTK / ParaView will be searched if installed and will not be build locally." OFF)
-if(NOT OGS_DONT_USE_VTK)
-	include(scripts/cmake/ExternalProjectCatalyst.cmake)
-endif()
+include(scripts/cmake/ExternalProjectCatalyst.cmake)
 
 include_directories( SYSTEM ${Boost_INCLUDE_DIRS} )
 if(OGS_USE_EIGEN)
@@ -151,9 +145,7 @@ if(TARGET Boost)
 endif()
 add_subdirectory( FileIO )
 add_subdirectory( GeoLib )
-if(NOT OGS_DONT_USE_VTK)
-	add_subdirectory( InSituLib )
-endif()
+add_subdirectory( InSituLib )
 add_subdirectory( MathLib )
 add_subdirectory( MeshLib )
 add_subdirectory( MeshGeoToolsLib )
diff --git a/FileIO/CMakeLists.txt b/FileIO/CMakeLists.txt
index 97b3da8b0249f9a3d936033d06312ec019927388..ffa5960e411bf3dc364ac0b2113a08dd6a9f9ea9 100644
--- a/FileIO/CMakeLists.txt
+++ b/FileIO/CMakeLists.txt
@@ -26,9 +26,7 @@ set(SOURCES
 GET_SOURCE_FILES(SOURCES_LEGACY Legacy)
 GET_SOURCE_FILES(SOURCES_GMSHIO GmshIO)
 GET_SOURCE_FILES(SOURCES_RAPID_XML RapidXmlIO)
-if(NOT OGS_DONT_USE_VTK)
-	GET_SOURCE_FILES(SOURCES_VTK VtkIO)
-endif()
+GET_SOURCE_FILES(SOURCES_VTK VtkIO)
 set(SOURCES ${SOURCES} ${SOURCES_LEGACY} ${SOURCES_GMSHIO} ${SOURCES_RAPID_XML} ${SOURCES_VTK})
 
 GET_SOURCE_FILES(SOURCES_BASE_XML XmlIO)
diff --git a/FileIO/readMeshFromFile.cpp b/FileIO/readMeshFromFile.cpp
index 36e34574c5b1016c3f1a277175de8614cb747afb..a82880078563719d77c6af400bb0a2dba8518a0d 100644
--- a/FileIO/readMeshFromFile.cpp
+++ b/FileIO/readMeshFromFile.cpp
@@ -31,9 +31,7 @@
 
 // FileIO
 #include "Legacy/MeshIO.h"
-#ifndef OGS_DONT_USE_VTK
 #include "FileIO/VtkIO/VtuInterface.h"
-#endif
 #include "readMeshFromFile.h"
 // FileIO : for reading partitioned mesh.
 #ifdef USE_PETSC
@@ -55,10 +53,8 @@ MeshLib::Mesh* readMeshFromFile(const std::string &file_name)
 		return meshIO.loadMeshFromFile(file_name);
 	}
 
-#ifndef OGS_DONT_USE_VTK
 	if (BaseLib::hasFileExtension("vtu", file_name))
 		return VtuInterface::readVTUFile(file_name);
-#endif
 
 	ERR("readMeshFromFile(): Unknown mesh file format in file %s.", file_name.c_str());
 	return nullptr;
diff --git a/FileIO/writeMeshToFile.cpp b/FileIO/writeMeshToFile.cpp
index 9ec13b71119bd3a82b33cd9491b286c6dcfef8d8..f4b907f20c8ba521d24bbd514af7d34b06de782e 100644
--- a/FileIO/writeMeshToFile.cpp
+++ b/FileIO/writeMeshToFile.cpp
@@ -20,9 +20,7 @@
 
 // FileIO
 #include "Legacy/MeshIO.h"
-#ifndef OGS_DONT_USE_VTK
 #include "FileIO/VtkIO/VtuInterface.h"
-#endif
 
 namespace FileIO
 {
@@ -33,11 +31,9 @@ void writeMeshToFile(const MeshLib::Mesh &mesh, const std::string &file_name)
 		Legacy::MeshIO meshIO;
 		meshIO.setMesh(&mesh);
 		meshIO.writeToFile(file_name);
-#ifndef OGS_DONT_USE_VTK
 	} else if (BaseLib::hasFileExtension("vtu", file_name)) {
 		FileIO::VtuInterface writer(&mesh);
 		writer.writeToFile(file_name);
-#endif
 	} else {
 		ERR("writeMeshToFile(): Unknown mesh file format in file %s.", file_name.c_str());
 	}
diff --git a/MeshLib/CMakeLists.txt b/MeshLib/CMakeLists.txt
index a22d156541e1ef1444e4a22e761bd6b9dc9c7cb7..8a41843600ceebc3a5a1ef962f4688542f3e3614 100644
--- a/MeshLib/CMakeLists.txt
+++ b/MeshLib/CMakeLists.txt
@@ -9,10 +9,6 @@ endif()
 GET_SOURCE_FILES(SOURCES_ELEMENTS Elements)
 GET_SOURCE_FILES(SOURCES_EDITING MeshEditing)
 GET_SOURCE_FILES(SOURCES_GENERATORS MeshGenerators)
-if(OGS_DONT_USE_VTK)
-	list(REMOVE_ITEM SOURCES_GENERATORS MeshGenerators/VtkMeshConverter.h)
-	list(REMOVE_ITEM SOURCES_GENERATORS MeshGenerators/VtkMeshConverter.cpp)
-endif()
 
 GET_SOURCE_FILES(SOURCES_QUALITY MeshQuality)
 set(SOURCES ${SOURCES_MESHLIB} ${SOURCES_ELEMENTS} ${SOURCES_EDITING} ${SOURCES_GENERATORS} ${SOURCES_QUALITY})
diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index ea93266e425669f0d95dafb5519443d36e6253f0..63bd0d05878f18d76fb832a3b0943b898fd3bf59 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -8,14 +8,12 @@ APPEND_SOURCE_FILES(TEST_SOURCES)
 APPEND_SOURCE_FILES(TEST_SOURCES AssemblerLib)
 APPEND_SOURCE_FILES(TEST_SOURCES BaseLib)
 APPEND_SOURCE_FILES(TEST_SOURCES GeoLib)
-if(NOT OGS_DONT_USE_VTK)
-	APPEND_SOURCE_FILES(TEST_SOURCES InSituLib)
-endif()
+APPEND_SOURCE_FILES(TEST_SOURCES InSituLib)
 APPEND_SOURCE_FILES(TEST_SOURCES MathLib)
 APPEND_SOURCE_FILES(TEST_SOURCES MeshLib)
 APPEND_SOURCE_FILES(TEST_SOURCES NumLib)
 
-set(TEST_SOURCES ${TEST_SOURCES} 
+set(TEST_SOURCES ${TEST_SOURCES}
 	FileIO/TestGLIReader.cpp
 	FileIO/TestCsvReader.cpp
 )
@@ -53,6 +51,7 @@ target_link_libraries(testrunner
 	BaseLib
 	FileIO
 	GeoLib
+	InSituLib
 	MathLib
 	MeshLib
 	MeshGeoToolsLib
@@ -60,14 +59,10 @@ target_link_libraries(testrunner
 	logog
 	${BOOST_LIBRARIES}
 	${CMAKE_THREAD_LIBS_INIT}
+	${CATALYST_LIBRARIES}
 )
-if(NOT OGS_DONT_USE_VTK)
-	target_link_libraries(testrunner
-		InSituLib
-		${CATALYST_LIBRARIES}
-	)
-	ADD_CATALYST_DEPENDENCY(testrunner)
-endif()
+ADD_CATALYST_DEPENDENCY(testrunner)
+
 if(OGS_USE_PETSC)
 	target_link_libraries(testrunner ${PETSC_LIBRARIES})
 endif()