diff --git a/src/libopensc/padding.c b/src/libopensc/padding.c
index b9dbd31d..798ae6ef 100644
--- a/src/libopensc/padding.c
+++ b/src/libopensc/padding.c
@@ -225,7 +225,8 @@ int sc_pkcs1_encode(struct sc_context *ctx, unsigned long flags,
 	switch(pad_algo) {
 	case SC_ALGORITHM_RSA_PAD_NONE:
 		/* padding done by card => nothing to do */
-		memcpy(out, tmp, tmp_len);
+		if (out != tmp)
+			memcpy(out, tmp, tmp_len);
 		*out_len = tmp_len;
 		return SC_SUCCESS;
 	case SC_ALGORITHM_RSA_PAD_PKCS1: