diff --git a/msvc/ecl/config.h.msvc6 b/msvc/ecl/config.h.msvc6
index 1d7904163..4e3d03978 100644
--- a/msvc/ecl/config.h.msvc6
+++ b/msvc/ecl/config.h.msvc6
@@ -13,6 +13,30 @@
     See file '../Copyright' for full details.
 */
 
+/*
+ * If ECL_API has been predefined, that means we are building the core
+ * library and, under windows, we must tell the compiler to export
+ * extern functions from the shared library.
+ * If ECL_API is not defined, we are simply building an application that
+ * uses ECL and, under windows, we must tell the compiler that certain
+ * will be imported from a DLL.
+ */
+#if defined(mingw32) || defined(_MSC_VER) || defined(cygwin)
+# define ECL_DLLEXPORT __declspec(dllexport)
+# ifdef ECL_API
+#  undef ECL_API
+#  define ECL_API __declspec(dllexport)
+# else
+#  define ECL_API __declspec(dllimport)
+# endif
+#else
+# define ECL_DLLEXPORT
+# ifdef ECL_API
+#  undef ECL_API
+# endif
+# define ECL_API
+#endif
+
 /*
  * FEATURES LINKED IN
  */