diff --git a/ports/unix/variants/wasi/mpconfigvariant.h b/ports/unix/variants/wasi/mpconfigvariant.h
index 75201e9abc..e54ba42cf3 100644
--- a/ports/unix/variants/wasi/mpconfigvariant.h
+++ b/ports/unix/variants/wasi/mpconfigvariant.h
@@ -27,5 +27,8 @@
 // Set base feature level.
 #define MICROPY_CONFIG_ROM_LEVEL (MICROPY_CONFIG_ROM_LEVEL_EXTRA_FEATURES)
 
+// WASI has different values for POLL constants.
+#define MICROPY_PY_SELECT_POSIX_OPTIMISATIONS (0)
+
 // Enable extra Unix features.
 #include "../mpconfigvariant_common.h"