diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index 623db76f5..5a5bc6e8d 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -227,7 +227,9 @@ int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, s
     /*
      * Prepare signature
      */
-    mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c, len, hash );
+    ret = mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c, len, hash );
+    if( ret != 0 )
+        return( ret );
 
     if( ( ret = mbedtls_pk_sign( ctx->key, ctx->md_alg, hash, 0, sig, &sig_len,
                                  f_rng, p_rng ) ) != 0 )