diff --git a/nix-rust/local.mk b/nix-rust/local.mk
index ce88fa51b..a5e017cef 100644
--- a/nix-rust/local.mk
+++ b/nix-rust/local.mk
@@ -4,6 +4,6 @@ libnixrust_LDFLAGS_USE := -L$(d)/target/release -lnixrust -ldl
 libnixrust_LDFLAGS_USE_INSTALLED := $(libnixrust_LDFLAGS_USE)
 
 $(d)/target/release/libnixrust.a: $(wildcard $(d)/src/*.rs) $(d)/Cargo.toml
-	$(trace-gen) cd nix-rust && CARGO_HOME=$$(if [[ -d vendor ]]; then echo vendor; fi) cargo build --release -Z offline && touch target/release/libnixrust.a
+	$(trace-gen) cd nix-rust && CARGO_HOME=$$(if [[ -d vendor ]]; then echo vendor; fi) cargo build --release $$(if [[ -d vendor ]]; then echo -Z offline; fi) && touch target/release/libnixrust.a
 
 dist-files += $(d)/vendor