diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index 7541fae..f06e709 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -1185,6 +1185,7 @@
     TEST_EQUAL( mbedtls_ecp_tls_read_group_id( &read_g_id, &vbuf, olen ),
                 0 );
     TEST_EQUAL( read_g_id, id );
+    vbuf = buf;
     TEST_EQUAL( mbedtls_ecp_tls_read_group( &grp_read, &vbuf, olen ),
                 0 );
     TEST_EQUAL( grp_read.id, id );