diff --git a/tests/run/pure_py.py b/tests/run/pure_py.py
index 2d3443162360446d379b807467f2abb456dae35c..4b28608163f6292121a8b55b1cc770362cec598f 100644
--- a/tests/run/pure_py.py
+++ b/tests/run/pure_py.py
@@ -39,7 +39,7 @@ def test_declare(n):
     y = cython.declare(cython.int, n)
     if cython.compiled:
         cython.declare(xx=cython.int, yy=cython.long)
-        i = sizeof(xx)
+        i = cython.sizeof(xx)
     ptr = cython.declare(cython.p_int, cython.address(y))
     return y, ptr[0]