diff --git a/library/constant_time.c b/library/constant_time.c
index d01998b..2b62bc1 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -708,7 +708,8 @@
                                 mbedtls_mpi *Y,
                                 unsigned char swap )
 {
-    int ret, s;
+    int ret = 0;
+    int s;
     MPI_VALIDATE_RET( X != NULL );
     MPI_VALIDATE_RET( Y != NULL );