diff --git a/CMakeLists.txt b/CMakeLists.txt
index ec93d7091b9a707db495050889f7fe532d124889..87ff45bb1bc365b589ca6fc9c3f19b22d62440a3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -136,7 +136,11 @@ set(GMSH_API
   contrib/HighOrderMeshOptimizer/OptHOM.h contrib/HighOrderMeshOptimizer/OptHomMesh.h
   contrib/HighOrderMeshOptimizer/OptHomRun.h contrib/HighOrderMeshOptimizer/ParamCoord.h
   contrib/HighOrderMeshOptimizer/OptHomFastCurving.h contrib/HighOrderMeshOptimizer/SuperEl.h
-  contrib/MathEx/mathex.h PARENT_SCOPE)
+  contrib/MathEx/mathex.h)
+
+if(PARENT_DIRECTORY)
+  set(GMSH_API ${GMSH_API} PARENT_SCOPE)
+endif(PARENT_DIRECTORY)
 
 execute_process(COMMAND date "+%Y%m%d" OUTPUT_VARIABLE DATE 
                 OUTPUT_STRIP_TRAILING_WHITESPACE)