diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index 089d441e91..e03442c120 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -9,7 +9,9 @@
 # by the Free Software Foundation.
 # See the COPYING file for more information.
 ################################################################################
+
 file(GLOB_RECURSE _sources ${CMAKE_CURRENT_LIST_DIR}/*.cpp CONFIGURE_DEPEND)
+set_source_files_properties(${_sources} PROPERTIES COMPILE_FLAGS -O1)
 add_executable(test_geos_unit ${_sources})
 unset(_sources)