all: Use MP_ERROR_TEXT for all error messages.
diff --git a/py/modstruct.c b/py/modstruct.c
index caf0ad9..4cbcad6 100644
--- a/py/modstruct.c
+++ b/py/modstruct.c
@@ -141,7 +141,7 @@
             // negative offsets are relative to the end of the buffer
             offset = bufinfo.len + offset;
             if (offset < 0) {
-                mp_raise_ValueError("buffer too small");
+                mp_raise_ValueError(MP_ERROR_TEXT("buffer too small"));
             }
         }
         p += offset;
@@ -150,7 +150,7 @@
 
     // Check that the input buffer is big enough to unpack all the values
     if (p + total_sz > end_p) {
-        mp_raise_ValueError("buffer too small");
+        mp_raise_ValueError(MP_ERROR_TEXT("buffer too small"));
     }
 
     for (size_t i = 0; i < num_items;) {
@@ -232,7 +232,7 @@
         // negative offsets are relative to the end of the buffer
         offset = (mp_int_t)bufinfo.len + offset;
         if (offset < 0) {
-            mp_raise_ValueError("buffer too small");
+            mp_raise_ValueError(MP_ERROR_TEXT("buffer too small"));
         }
     }
     byte *p = (byte *)bufinfo.buf;
@@ -242,7 +242,7 @@
     // Check that the output buffer is big enough to hold all the values
     mp_int_t sz = MP_OBJ_SMALL_INT_VALUE(struct_calcsize(args[0]));
     if (p + sz > end_p) {
-        mp_raise_ValueError("buffer too small");
+        mp_raise_ValueError(MP_ERROR_TEXT("buffer too small"));
     }
 
     struct_pack_into_internal(args[0], p, n_args - 3, &args[3]);