diff --git a/config/makefiles/rust.mk b/config/makefiles/rust.mk
--- a/config/makefiles/rust.mk
+++ b/config/makefiles/rust.mk
@@ -10,6 +10,10 @@
 # commands can be executed directly by make, without doing a round-trip
 # through a shell.
 
+MOZ_MAKE_FLAGS := $(filter-out -j%,$(MAKEFLAGS))
+MAKEFLAGS += -j1
+
+
 cargo_host_flag := --target=$(RUST_HOST_TARGET)
 cargo_target_flag := --target=$(RUST_TARGET)