py/builtinimport: Raise ValueError for bad relative import, per CPython.
diff --git a/py/builtinimport.c b/py/builtinimport.c
index 4024c5d..0e3f160 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -360,8 +360,7 @@
         qstr new_mod_q = qstr_from_strn(new_mod, new_mod_l);
         DEBUG_printf("Resolved base name for relative import: '%s'\n", qstr_str(new_mod_q));
         if (new_mod_q == MP_QSTR_) {
-            // CPython raises SystemError
-            mp_raise_msg(&mp_type_ImportError, "cannot perform relative import");
+            mp_raise_msg(&mp_type_ValueError, "cannot perform relative import");
         }
         module_name = MP_OBJ_NEW_QSTR(new_mod_q);
         mod_str = new_mod;