diff --git a/library/rsa.c b/library/rsa.c
index a25c633..0007546 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1106,10 +1106,10 @@
     mbedtls_mpi_free( &C );
     mbedtls_mpi_free( &I );
 
-    if( ret != 0 )
+    if( ret != 0 && ret >= -0x007f )
         return( MBEDTLS_ERR_RSA_PRIVATE_FAILED + ret );
 
-    return( 0 );
+    return( ret );
 }
 
 #if defined(MBEDTLS_PKCS1_V21)