diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-10-30-13-11-01.bpo-42206.xxssR8.rst b/Misc/NEWS.d/next/Core and Builtins/2020-10-30-13-11-01.bpo-42206.xxssR8.rst
new file mode 100644
index 00000000000..b9eb135fec5
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-10-30-13-11-01.bpo-42206.xxssR8.rst	
@@ -0,0 +1,2 @@
+Propagate and raise the errors caused by :c:func:`PyAST_Validate` in the
+parser.
diff --git a/Parser/pegen.c b/Parser/pegen.c
index 827d4dace1f..216edd810e2 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -1157,7 +1157,9 @@ _PyPegen_run_parser(Parser *p)
         p->start_rule == Py_file_input ||
         p->start_rule == Py_eval_input)
     {
-        assert(PyAST_Validate(res));
+        if (!PyAST_Validate(res)) {
+            return NULL;
+        }
     }
 #endif
     return res;