diff --git a/ports/unix/variants/mpconfigvariant_common.h b/ports/unix/variants/mpconfigvariant_common.h
index 030fbcb0c0..4b0fa4e228 100644
--- a/ports/unix/variants/mpconfigvariant_common.h
+++ b/ports/unix/variants/mpconfigvariant_common.h
@@ -91,7 +91,9 @@
 #define MICROPY_PY_OS_ERRNO            (1)
 #define MICROPY_PY_OS_GETENV_PUTENV_UNSETENV (1)
 #define MICROPY_PY_OS_SEP              (1)
+#ifndef MICROPY_PY_OS_SYSTEM
 #define MICROPY_PY_OS_SYSTEM           (1)
+#endif
 #define MICROPY_PY_OS_URANDOM          (1)
 
 // Enable the unix-specific "time" module.