diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 6f5abf3b8..d023466eb 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -337,7 +337,7 @@ void mbedtls_mpi_lt_mpi_ct( int size_X, char * input_X,
                             int size_Y, char * input_Y,
                             int input_ret, int input_err )
 {
-    unsigned ret;
+    unsigned ret = -1;
     unsigned input_uret = input_ret;
     mbedtls_mpi X, Y;
     mbedtls_mpi_init( &X ); mbedtls_mpi_init( &Y );