diff --git a/rules.mk b/rules.mk
index 28e6a41..893dbc6 100644
--- a/rules.mk
+++ b/rules.mk
@@ -10,6 +10,12 @@ MODULE_SRCS := \
 MODULE_RUST_EDITION := 2018
 MODULE_RUSTFLAGS += \
 	--cfg 'feature="default"' \
+
+ifeq ($(call TOBOOL,$(TRUSTY_USERSPACE)),true)
+
+MODULE_RUSTFLAGS += \
 	--cfg 'feature="std"' \
 
+endif
+
 include make/library.mk