1diff --git a/rules.mk b/rules.mk
2index d9b6b71f..1bb39ffc 100644
3--- a/rules.mk
4+++ b/rules.mk
5@@ -8,17 +8,26 @@ MODULE := $(LOCAL_DIR)
6 MODULE_CRATE_NAME := once_cell
7 MODULE_RUST_CRATE_TYPES := rlib
8 MODULE_SRCS := $(LOCAL_DIR)/src/lib.rs
9-MODULE_ADD_IMPLICIT_DEPS := false
10 MODULE_RUST_EDITION := 2021
11 MODULE_RUSTFLAGS += \
12 	--cfg 'feature="alloc"' \
13 	--cfg 'feature="default"' \
14 	--cfg 'feature="race"' \
15-	--cfg 'feature="std"'
16+
17+ifeq ($(call TOBOOL,$(TRUSTY_USERSPACE)),true)
18+
19+MODULE_RUSTFLAGS += \
20+	--cfg 'feature="std"' \
21+
22+else
23+
24+MODULE_ADD_IMPLICIT_DEPS := false
25
26 MODULE_LIBRARY_DEPS := \
27 	trusty/user/base/lib/liballoc-rust \
28 	trusty/user/base/lib/libcompiler_builtins-rust \
29 	trusty/user/base/lib/libcore-rust
30
31+endif
32+
33 include make/library.mk
34