diff --git a/tests/cpydiff/syntax_assign_expr.py b/tests/cpydiff/syntax_assign_expr.py
new file mode 100644
index 0000000000..d4ed063b39
--- /dev/null
+++ b/tests/cpydiff/syntax_assign_expr.py
@@ -0,0 +1,7 @@
+"""
+categories: Syntax,Operators
+description: MicroPython allows using := to assign to the variable of a comprehension, CPython raises a SyntaxError.
+cause: MicroPython is optimised for code size and doesn't check this case.
+workaround: Do not rely on this behaviour if writing CPython compatible code.
+"""
+print([i := -1 for i in range(4)])