diff --git a/hpy/universal/src/hpymodule.c b/hpy/universal/src/hpymodule.c
index 1da0bc036..cd2ba5e9c 100644
--- a/hpy/universal/src/hpymodule.c
+++ b/hpy/universal/src/hpymodule.c
@@ -14,17 +14,14 @@
 #include "hpy_debug.h"
 
 #ifdef PYPY_VERSION
-#  error "Cannot build hpy.univeral on top of PyPy. PyPy comes with its own version of it"
+#  error "Cannot build hpy.universal on top of PyPy. PyPy comes with its own version of it"
+#endif
+#ifdef GRAALVM_PYTHON
+#  error "Cannot build hpy.universal on top of GraalPython. GraalPython comes with its own version of it"
 #endif
 
 typedef HPy (*InitFuncPtr)(HPyContext *ctx);
 
-static PyObject *set_debug(PyObject *self, PyObject *args)
-{
-    // TODO
-    Py_RETURN_NONE;
-}
-
 static const char *prefix = "HPyInit";
 
 static HPyContext * get_context(int debug)
@@ -101,8 +98,10 @@ static PyObject *do_load(PyObject *name_unicode, PyObject *path, int debug)
     if (mylib == NULL) {
         const char *error = dlerror();
         if (error == NULL)
-            error = "unknown dlopen() error";
-        PyErr_Format(PyExc_RuntimeError, "dlopen: %s", error);
+            error = "no error message provided by the system";
+        PyErr_Format(PyExc_RuntimeError,
+                     "Error during loading of the HPy extension module at path "
+                     "'%s'. Error message from dlopen/WinAPI: %s", soname, error);
         goto error;
     }
 
@@ -110,8 +109,12 @@ static PyObject *do_load(PyObject *name_unicode, PyObject *path, int debug)
     if (initfn == NULL) {
         const char *error = dlerror();
         if (error == NULL)
-            error = "unknown dlsym() error";
-        PyErr_Format(PyExc_RuntimeError, "dlsym: %s", error);
+            error = "no error message provided by the system";
+        PyErr_Format(PyExc_RuntimeError,
+                     "Error during loading of the HPy extension module at "
+                     "path '%s' while trying to find symbol '%s'. Did you use"
+                     "the HPy_MODINIT macro to register your module? Error "
+                     "message from dlsym/WinAPI: %s", soname, init_name, error);
         goto error;
     }
 
@@ -152,7 +155,6 @@ static PyObject *get_version(PyObject *self, PyObject *ignored)
 }
 
 static PyMethodDef HPyMethods[] = {
-    {"set_debug", (PyCFunction)set_debug, METH_O, "TODO"},
     {"load", (PyCFunction)load, METH_VARARGS | METH_KEYWORDS, "Load a .hpy.so"},
     {"get_version", (PyCFunction)get_version, METH_NOARGS, "Return a tuple ('version', 'git revision')"},
     {NULL, NULL, 0, NULL}