diff --git a/libsrc/include/nginterface.h b/libsrc/include/nginterface.h
index bbdd267c..c09f18f0 100644
--- a/libsrc/include/nginterface.h
+++ b/libsrc/include/nginterface.h
@@ -18,18 +18,12 @@
 
 */
 
-#ifdef WIN32
-   #if NGINTERFACE_EXPORTS || NGLIB_EXPORTS || nglib_EXPORTS
-      #define DLL_HEADER   __declspec(dllexport)
-   #else
-      #define DLL_HEADER   __declspec(dllimport)
-   #endif
-#else
-   #if __GNUC__ >= 4
-      #define DLL_HEADER __attribute__ ((visibility ("default")))
-   #else
-      #define DLL_HEADER
-   #endif
+#ifndef DLL_HEADER
+  #if NGINTERFACE_EXPORTS || NGLIB_EXPORTS || nglib_EXPORTS
+    #define DLL_HEADER NGCORE_API_EXPORT
+  #else
+    #define DLL_HEADER NGCORE_API_IMPORT
+  #endif
 #endif
 
 
diff --git a/nglib/nglib.h b/nglib/nglib.h
index 8a78da07..286db0cb 100644
--- a/nglib/nglib.h
+++ b/nglib/nglib.h
@@ -23,6 +23,7 @@
 
 // Philippose - 14.02.2009
 // Modifications for creating a DLL in Windows
+#ifndef DLL_HEADER
 #ifdef WIN32
    #ifdef NGLIB_EXPORTS || nglib_EXPORTS
       #define DLL_HEADER   __declspec(dllexport)
@@ -30,9 +31,9 @@
       #define DLL_HEADER   __declspec(dllimport)
    #endif
 #else
-   #define DLL_HEADER 
+  #define DLL_HEADER __attribute__((visibility("default")))
+#endif
 #endif
-
 
 
 // ** Constants used within Netgen *********************