diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-07-20-12-21-37.gh-issue-105699.08ywGV.rst b/Misc/NEWS.d/next/Core and Builtins/2023-07-20-12-21-37.gh-issue-105699.08ywGV.rst
new file mode 100644
index 00000000000000..82312718cd047e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-07-20-12-21-37.gh-issue-105699.08ywGV.rst	
@@ -0,0 +1,4 @@
+Python no longer crashes due to an infrequent race in setting
+``Py_FileSystemDefaultEncoding`` and ``Py_FileSystemDefaultEncodeErrors``
+(both deprecated), when simultaneously initializing two isolated
+subinterpreters.  Now they are only set during runtime initialization.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index a0be85718119de..cd196f5b11cd9a 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -15177,10 +15177,13 @@ init_fs_codec(PyInterpreterState *interp)
 
     /* Set Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors
        global configuration variables. */
-    if (_Py_SetFileSystemEncoding(fs_codec->encoding,
-                                  fs_codec->errors) < 0) {
-        PyErr_NoMemory();
-        return -1;
+    if (_Py_IsMainInterpreter(interp)) {
+
+        if (_Py_SetFileSystemEncoding(fs_codec->encoding,
+                                      fs_codec->errors) < 0) {
+            PyErr_NoMemory();
+            return -1;
+        }
     }
     return 0;
 }