diff --git a/Framework/Geometry/CMakeLists.txt b/Framework/Geometry/CMakeLists.txt
index 87cff330545940988b6e1270e0fb65f0fd5f477a..5af0477e18a175d331c8ae201a369c81c5d14e1c 100644
--- a/Framework/Geometry/CMakeLists.txt
+++ b/Framework/Geometry/CMakeLists.txt
@@ -442,7 +442,7 @@ endif(UNITY_BUILD)
 
 # ===================== Open Cascade ===================
 if (ENABLE_OPENCASCADE)
-  set (SRC_FILES ${SRC_FILES} ${OPENCASCADE_SRC} )
+  LIST (APPEND SRC_FILES ${OPENCASCADE_SRC} )
 endif ()
 
 # A few defines needed for OpenCascade on the Mac