diff --git a/Lib/distutils/command/install_lib.py b/Lib/distutils/command/install_lib.py
index 87e3c7aa04a..411db79cc24 100644
--- a/Lib/distutils/command/install_lib.py
+++ b/Lib/distutils/command/install_lib.py
@@ -80,7 +80,8 @@ def finalize_options(self):
         if not isinstance(self.optimize, int):
             try:
                 self.optimize = int(self.optimize)
-                assert self.optimize in (0, 1, 2)
+                if self.optimize not in (0, 1, 2):
+                    raise AssertionError
             except (ValueError, AssertionError):
                 raise DistutilsOptionError, "optimize must be 0, 1, or 2"