diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index 7786cca35..39de4fe42 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -522,7 +522,7 @@ if(ENABLE_UNIT_TESTING)
     if(ENABLE_UNIT_TESTING_EXTRA)
         target_link_libraries(run_tests PRIVATE Gpstk::gpstk)
         if(GPSTK_OLDER_THAN_8)
-	        target_compile_definitions(run_tests PRIVATE -DOLD_GPSTK=1)
+            target_compile_definitions(run_tests PRIVATE -DOLD_GPSTK=1)
         endif()
     endif()
     if(ENABLE_STRIP)