diff --git a/Parser/pegen/parse.c b/Parser/pegen/parse.c
index 2b735472ad6..b63924177d4 100644
--- a/Parser/pegen/parse.c
+++ b/Parser/pegen/parse.c
@@ -1,7 +1,7 @@
 // @generated by pegen.py from ./Grammar/python.gram
 #include "pegen.h"
 
-#ifdef Py_DEBUG
+#if defined(Py_DEBUG) && defined(Py_BUILD_CORE)
 extern int Py_DebugFlag;
 #define D(x) if (Py_DebugFlag) x;
 #else
diff --git a/Tools/peg_generator/pegen/c_generator.py b/Tools/peg_generator/pegen/c_generator.py
index ff7e75a9fdf..8bc23911bbb 100644
--- a/Tools/peg_generator/pegen/c_generator.py
+++ b/Tools/peg_generator/pegen/c_generator.py
@@ -29,7 +29,7 @@ from pegen.parser_generator import ParserGenerator
 EXTENSION_PREFIX = """\
 #include "pegen.h"
 
-#ifdef Py_DEBUG
+#if defined(Py_DEBUG) && defined(Py_BUILD_CORE)
 extern int Py_DebugFlag;
 #define D(x) if (Py_DebugFlag) x;
 #else