diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
index 1bb80f970..e42ad5e49 100644
--- a/ports/unix/mpconfigport.h
+++ b/ports/unix/mpconfigport.h
@@ -70,6 +70,7 @@
 #ifndef MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE
 #define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (1)
 #endif
+#define MICROPY_MODULE_WEAK_LINKS   (1)
 #define MICROPY_CAN_OVERRIDE_BUILTINS (1)
 #define MICROPY_PY_FUNCTION_ATTRS   (1)
 #define MICROPY_PY_DESCRIPTORS      (1)
diff --git a/ports/windows/mpconfigport.h b/ports/windows/mpconfigport.h
index 1a9842609..fae01d74e 100644
--- a/ports/windows/mpconfigport.h
+++ b/ports/windows/mpconfigport.h
@@ -60,6 +60,7 @@
 #define MICROPY_STREAMS_POSIX_API   (1)
 #define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (1)
+#define MICROPY_MODULE_WEAK_LINKS   (1)
 #define MICROPY_CAN_OVERRIDE_BUILTINS (1)
 #define MICROPY_PY_FUNCTION_ATTRS   (1)
 #define MICROPY_PY_DESCRIPTORS      (1)