diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 52fcd70..8261b1c 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -24,3 +24,5 @@ else()                          # Catch 1.x
       "Neither Catch 2.x nor Catch 1.x could be found.")
   endif()
 endif()
+
+unset(sources_tests)