diff --git a/py/compile.c b/py/compile.c
index 4e704ab..ee01749 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -1050,8 +1050,8 @@
             for (int i = 0; i < n; i++) {
                 len += qstr_len(MP_PARSE_NODE_LEAF_ARG(pns->nodes[i]));
             }
-            byte *q_ptr;
-            byte *str_dest = qstr_build_start(len, &q_ptr);
+            char *q_ptr = alloca(len);
+            char *str_dest = q_ptr;
             for (int i = 0; i < n; i++) {
                 if (i > 0) {
                     *str_dest++ = '.';
@@ -1061,7 +1061,7 @@
                 memcpy(str_dest, str_src, str_src_len);
                 str_dest += str_src_len;
             }
-            qstr q_full = qstr_build_end(q_ptr);
+            qstr q_full = qstr_from_strn(q_ptr, len);
             EMIT_ARG(import_name, q_full);
             if (is_as) {
                 for (int i = 1; i < n; i++) {
diff --git a/py/qstr.c b/py/qstr.c
index 95c9b68..a3c9612 100644
--- a/py/qstr.c
+++ b/py/qstr.c
@@ -243,29 +243,6 @@
     return q;
 }
 
-byte *qstr_build_start(size_t len, byte **q_ptr) {
-    assert(len < (1 << (8 * MICROPY_QSTR_BYTES_IN_LEN)));
-    *q_ptr = m_new(byte, MICROPY_QSTR_BYTES_IN_HASH + MICROPY_QSTR_BYTES_IN_LEN + len + 1);
-    Q_SET_LENGTH(*q_ptr, len);
-    return Q_GET_DATA(*q_ptr);
-}
-
-qstr qstr_build_end(byte *q_ptr) {
-    QSTR_ENTER();
-    qstr q = qstr_find_strn((const char*)Q_GET_DATA(q_ptr), Q_GET_LENGTH(q_ptr));
-    if (q == 0) {
-        size_t len = Q_GET_LENGTH(q_ptr);
-        mp_uint_t hash = qstr_compute_hash(Q_GET_DATA(q_ptr), len);
-        Q_SET_HASH(q_ptr, hash);
-        q_ptr[MICROPY_QSTR_BYTES_IN_HASH + MICROPY_QSTR_BYTES_IN_LEN + len] = '\0';
-        q = qstr_add(q_ptr);
-    } else {
-        m_del(byte, q_ptr, Q_GET_ALLOC(q_ptr));
-    }
-    QSTR_EXIT();
-    return q;
-}
-
 mp_uint_t qstr_hash(qstr q) {
     return Q_GET_HASH(find_qstr(q));
 }
diff --git a/py/qstr.h b/py/qstr.h
index e2bdcc3..63fd0c3 100644
--- a/py/qstr.h
+++ b/py/qstr.h
@@ -65,9 +65,6 @@
 qstr qstr_from_str(const char *str);
 qstr qstr_from_strn(const char *str, size_t len);
 
-byte *qstr_build_start(size_t len, byte **q_ptr);
-qstr qstr_build_end(byte *q_ptr);
-
 mp_uint_t qstr_hash(qstr q);
 const char *qstr_str(qstr q);
 size_t qstr_len(qstr q);