diff --git a/py/compile.c b/py/compile.c
index 5b381e41d5..4aaa68e6ce 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -2776,6 +2776,8 @@ STATIC int compile_viper_type_annotation(compiler_t *comp, mp_parse_node_t pn_an
 #endif
 
 STATIC void compile_scope_func_lambda_param(compiler_t *comp, mp_parse_node_t pn, pn_kind_t pn_name, pn_kind_t pn_star, pn_kind_t pn_dbl_star) {
+    (void)pn_dbl_star;
+
     // check that **kw is last
     if ((comp->scope_cur->scope_flags & MP_SCOPE_FLAG_VARKEYWORDS) != 0) {
         compile_syntax_error(comp, pn, "invalid syntax");
diff --git a/py/emitnative.c b/py/emitnative.c
index a198ffb085..8b7ebe5301 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -2574,6 +2574,7 @@ STATIC void emit_native_return_value(emit_t *emit) {
 }
 
 STATIC void emit_native_raise_varargs(emit_t *emit, mp_uint_t n_args) {
+    (void)n_args;
     assert(n_args == 1);
     vtype_kind_t vtype_exc;
     emit_pre_pop_reg(emit, &vtype_exc, REG_ARG_1); // arg1 = object to raise
diff --git a/py/modio.c b/py/modio.c
index b4d033238f..0f4a4326ca 100644
--- a/py/modio.c
+++ b/py/modio.c
@@ -147,6 +147,7 @@ STATIC mp_uint_t bufwriter_write(mp_obj_t self_in, const void *buf, mp_uint_t si
         buf = (byte*)buf + rem;
         size -= rem;
         mp_uint_t out_sz = mp_stream_write_exactly(self->stream, self->buf, self->alloc, errcode);
+        (void)out_sz;
         if (*errcode != 0) {
             return MP_STREAM_ERROR;
         }
@@ -165,6 +166,7 @@ STATIC mp_obj_t bufwriter_flush(mp_obj_t self_in) {
     if (self->len != 0) {
         int err;
         mp_uint_t out_sz = mp_stream_write_exactly(self->stream, self->buf, self->len, &err);
+        (void)out_sz;
         // TODO: try to recover from a case of non-blocking stream, e.g. move
         // remaining chunk to the beginning of buffer.
         assert(out_sz == self->len);