diff --git a/config/RConfigure.in b/config/RConfigure.in
index bd886fbbf8735ccf72b0a0a1245546c71a37259a..ee8c0f4823375fd060798c27bc578c48171600f7 100644
--- a/config/RConfigure.in
+++ b/config/RConfigure.in
@@ -39,7 +39,9 @@
 #@useimt@ R__USE_IMT   /**/
 
 #if defined(R__HAS_VECCORE) && defined(R__HAS_VC)
+#ifndef VECCORE_ENABLE_VC
 #define VECCORE_ENABLE_VC
 #endif
+#endif
 
 #endif