Add configuration item for the PK module
diff --git a/library/pk.c b/library/pk.c
index e0a252f..0923afe 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -25,6 +25,8 @@
 
 #include "polarssl/config.h"
 
+#if defined(POLARSSL_PK_C)
+
 #include "polarssl/pk.h"
 #include "polarssl/pk_wrap.h"
 
@@ -251,3 +253,5 @@
 
     return( ctx->pk_info->name );
 }
+
+#endif /* POLARSSL_PK_C */