diff --git a/Source/kwsys/Base64.c b/Source/kwsys/Base64.c
index cdb0675fe..53d7c4618 100644
--- a/Source/kwsys/Base64.c
+++ b/Source/kwsys/Base64.c
@@ -14,7 +14,7 @@ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/
-#define KWSYS_IN_PROCESS_C
+#define KWSYS_IN_BASE64_C
 #include <Base64.h>
 
 /*--------------------------------------------------------------------------*/