--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -498,6 +498,7 @@ errfinish(const char *filename, int lineno, const char *funcname)

      elevel = edata->elevel;

+Assert(!(elevel == ERROR && edata->sqlerrcode == ERRCODE_INTERNAL_ERROR));
      /*
       * Do processing in ErrorContext, which we hope has enough reserved space
       * to report an error.