diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1009de3..361018b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,9 +12,9 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 include(cmake/CPM.cmake)
 CPMFindPackage(
     NAME tclap
-    GITHUB_REPOSITORY ufz/tclap
-    VERSION 1.2.4
-    GIT_TAG 098dd0fe07a31618f3c2a9f8727bb01c8c5d61e2
+    GIT_REPOSITORY https://git.code.sf.net/p/tclap/code
+    VERSION 1.4.0
+    GIT_TAG 81b3d2a0c47895c22e9bb8c577f5ab521f76e5d2
     DOWNLOAD_ONLY YES
 )
 if(tclap_ADDED AND NOT TARGET tclap)
diff --git a/vtkdiff.cpp b/vtkdiff.cpp
index d6568fb..c7782f8 100644
--- a/vtkdiff.cpp
+++ b/vtkdiff.cpp
@@ -110,7 +110,7 @@ auto parseCommandLine(int argc, char* argv[]) -> Args
     cmd.add(vtk_input_b_arg);
 
     TCLAP::ValueArg<std::string> data_array_a_arg(
-        "a", "first_data_array", "First data array name for comparison", true,
+        "a", "first_data_array", "First data array name for comparison", false,
         "", "NAME");
 
     TCLAP::ValueArg<std::string> data_array_b_arg(