diff --git a/Misc/NEWS b/Misc/NEWS
index 536712a..a8b5a3c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -152,6 +152,9 @@
 Library
 -------
 
+- Issue #5203: Fixed ctypes segfaults when passing a unicode string to a
+  function without argtypes (only occurs if HAVE_USABLE_WCHAR_T is false).
+
 - Issue #3386: distutils.sysconfig.get_python_lib prefix argument was ignored
   under NT and OS2. Patch by Philip Jenvey.
 
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index 7f7d641..8988c12 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -664,6 +664,7 @@
 		return 0;
 #else
 		int size = PyUnicode_GET_SIZE(obj);
+		pa->ffi_type = &ffi_type_pointer;
 		size += 1; /* terminating NUL */
 		size *= sizeof(wchar_t);
 		pa->value.p = PyMem_Malloc(size);