diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index afa9e61..b1c43b7 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -158,6 +158,10 @@
 #endif /* POLARSSL_HAVE_INT16 */
 #endif /* POLARSSL_HAVE_INT8  */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * \brief          MPI structure
  */
@@ -169,10 +173,6 @@
 }
 mpi;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  * \brief           Initialize one MPI
  *