diff --git a/cmake/AddFdbTest.cmake b/cmake/AddFdbTest.cmake
index 8a5068f21d..f5dbe64388 100644
--- a/cmake/AddFdbTest.cmake
+++ b/cmake/AddFdbTest.cmake
@@ -84,12 +84,19 @@ function(add_fdb_test)
   if (NOT "${ADD_FDB_TEST_TEST_NAME}" STREQUAL "")
     set(test_name ${ADD_FDB_TEST_TEST_NAME})
   endif()
+  math(EXPR test_idx "${CURRENT_TEST_INDEX} + 1")
+  set(CURRENT_TEST_INDEX "${test_idx}" PARENT_SCOPE)
+  # set(<var> <value> PARENT_SCOPE) doesn't set the
+  # value in this scope (only in the parent scope). So
+  # if the value was undefined before, it will still be
+  # undefined.
+  math(EXPR assigned_id "${test_idx} - 1")
   if(ADD_FDB_TEST_UNIT)
     message(STATUS
-      "ADDING UNIT TEST ${test_name}")
+      "ADDING UNIT TEST ${assigned_id} ${test_name}")
   else()
     message(STATUS
-      "ADDING SIMULATOR TEST ${test_name}")
+      "ADDING SIMULATOR TEST ${assigned_id} ${test_name}")
   endif()
   set(test_files "")
   foreach(curr_test_file ${ADD_FDB_TEST_TEST_FILES})
@@ -99,9 +106,6 @@ function(add_fdb_test)
   if (ENABLE_BUGGIFY)
     set(BUGGIFY_OPTION "-B")
   endif()
-  math(EXPR test_idx "${CURRENT_TEST_INDEX} + 1")
-  set(CURRENT_TEST_INDEX "${test_idx}" CACHE INTERNAL "The index used for the last added test" FORCE)
-  message("Added ${test_name} with idx ${CURRENT_TEST_INDEX}")
   list(TRANSFORM ADD_FDB_TEST_TEST_FILES PREPEND "${CMAKE_CURRENT_SOURCE_DIR}/")
   add_test(NAME ${test_name}
     COMMAND $<TARGET_FILE:Python::Interpreter> ${TestRunner}