diff -r 113cdce4663c Lib/test/test_cmd_line.py
--- a/Lib/test/test_cmd_line.py	Wed Jun 06 01:37:37 2012 +0200
+++ b/Lib/test/test_cmd_line.py	Wed Jun 06 01:50:05 2012 +0200
@@ -341,6 +341,18 @@ class CmdLineTest(unittest.TestCase):
         self.assertEqual(rc, 0)
         self.assertIn(b'random is 1', out)
 
+    def test_del___main__(self):
+        # Issue #15001: PyRun_SimpleFileExFlags() did crash because it kept a
+        # borrowed reference to the dict of __main__ module and later modify
+        # the dict whereas the module was destroyed
+        filename = test.support.TESTFN
+        self.addCleanup(test.support.unlink, filename)
+        with open(filename, "w") as script:
+            print("import sys", file=script)
+            print("del sys.modules['__main__']", file=script)
+        assert_python_ok(filename)
+
+
 def test_main():
     test.support.run_unittest(CmdLineTest)
     test.support.reap_children()
diff -r 113cdce4663c Python/pythonrun.c
--- a/Python/pythonrun.c	Wed Jun 06 01:37:37 2012 +0200
+++ b/Python/pythonrun.c	Wed Jun 06 01:50:05 2012 +0200
@@ -1323,25 +1323,26 @@ PyRun_SimpleFileExFlags(FILE *fp, const 
 {
     PyObject *m, *d, *v;
     const char *ext;
-    int set_file_name = 0, ret;
+    int set_file_name = 0, ret = -1;
     size_t len;
 
     m = PyImport_AddModule("__main__");
     if (m == NULL)
         return -1;
+    Py_INCREF(m);
     d = PyModule_GetDict(m);
     if (PyDict_GetItemString(d, "__file__") == NULL) {
         PyObject *f;
         f = PyUnicode_DecodeFSDefault(filename);
         if (f == NULL)
-            return -1;
+            goto done;
         if (PyDict_SetItemString(d, "__file__", f) < 0) {
             Py_DECREF(f);
-            return -1;
+            goto done;
         }
         if (PyDict_SetItemString(d, "__cached__", Py_None) < 0) {
             Py_DECREF(f);
-            return -1;
+            goto done;
         }
         set_file_name = 1;
         Py_DECREF(f);
@@ -1354,7 +1355,6 @@ PyRun_SimpleFileExFlags(FILE *fp, const 
             fclose(fp);
         if ((fp = fopen(filename, "rb")) == NULL) {
             fprintf(stderr, "python: Can't reopen .pyc file\n");
-            ret = -1;
             goto done;
         }
         /* Turn on optimization if a .pyo file is given */
@@ -1368,7 +1368,6 @@ PyRun_SimpleFileExFlags(FILE *fp, const 
     flush_io();
     if (v == NULL) {
         PyErr_Print();
-        ret = -1;
         goto done;
     }
     Py_DECREF(v);
@@ -1376,6 +1375,7 @@ PyRun_SimpleFileExFlags(FILE *fp, const 
   done:
     if (set_file_name && PyDict_DelItemString(d, "__file__"))
         PyErr_Clear();
+    Py_DECREF(m);
     return ret;
 }