diff --git a/modules/TDEMacros.cmake b/modules/TDEMacros.cmake
index 8ec1bcf..ceaea93 100644
--- a/modules/TDEMacros.cmake
+++ b/modules/TDEMacros.cmake
@@ -1072,7 +1072,7 @@ macro( tde_add_library _arg_target )
     endif( _embed AND  ${CMAKE_VERSION} VERSION_EQUAL "2.8.12.0" )
   endif( )
   if( _shared_libs )
-    string( TOUPPER ${CMAKE_BUILD_TYPE} _build_type )
+    string( TOUPPER "${CMAKE_BUILD_TYPE}" _build_type )
     set_target_properties( ${_target} PROPERTIES
                            LINK_INTERFACE_LIBRARIES "${_shared_libs}"
                            LINK_INTERFACE_LIBRARIES_${_build_type} "${_shared_libs}"