diff --git a/rules.mk b/rules.mk
index 11fd95b..cde5a71 100644
--- a/rules.mk
+++ b/rules.mk
@@ -11,7 +11,13 @@ MODULE_SRCS := $(LOCAL_DIR)/src/lib.rs
 MODULE_RUST_EDITION := 2018
 MODULE_RUSTFLAGS += \
 	--cfg 'feature="default"' \
-	--cfg 'feature="std"'
+
+ifeq ($(call TOBOOL,$(TRUSTY_USERSPACE)),true)
+
+MODULE_RUSTFLAGS += \
+	--cfg 'feature="std"' \
+
+endif

 MODULE_LIBRARY_DEPS := \