diff --git a/cross/syncstorage-rs/Makefile b/cross/syncstorage-rs/Makefile
index 6fe253d582e..e896c989cac 100644
--- a/cross/syncstorage-rs/Makefile
+++ b/cross/syncstorage-rs/Makefile
@@ -16,6 +16,8 @@ LICENSE  = https://github.com/mozilla-services/syncstorage-rs/blob/master/LICENS
 
 # arguments to install the main server program
 RUST_SRC_DIR = $(WORK_DIR)/$(PKG_DIR)/syncserver
-ENV += RUSTFLAGS="--no-default-features --features=syncstorage-db/mysql --locked"
+CARGO_BUILD_ARGS += --no-default-features
+CARGO_BUILD_ARGS += --features=syncstorage-db/mysql
+CARGO_BUILD_ARGS += --locked
 
 include ../../mk/spksrc.cross-rust.mk
diff --git a/mk/spksrc.cross-rust.mk b/mk/spksrc.cross-rust.mk
index e6385916b26..73c9e215885 100644
--- a/mk/spksrc.cross-rust.mk
+++ b/mk/spksrc.cross-rust.mk
@@ -53,10 +53,14 @@ endif
 CARGO_INSTALL_ARGS += --path $(RUST_SRC_DIR)
 CARGO_INSTALL_ARGS += --root $(STAGING_INSTALL_PREFIX)
 
+ifeq ($(strip $(CARGO_BUILD_ARGS)),)
+CARGO_BUILD_ARGS = 
+endif
+
 # Default build with rust and install with cargo
 rust_install_target:
 	@echo "  ==> Cargo install rust package $(PKG_NAME) ($(shell rustc --version); $(RUST_TOOLCHAIN))"
-	@$(RUN) cargo +$(RUST_TOOLCHAIN) install $(CARGO_INSTALL_ARGS)
+	@$(RUN) cargo +$(RUST_TOOLCHAIN) install $(CARGO_INSTALL_ARGS) $(CARGO_BUILD_ARGS)
 
 
 #####