diff --git a/mojo.mk b/mojo.mk
index f5cae37..f0cd518 100644
--- a/mojo.mk
+++ b/mojo.mk
@@ -68,7 +68,7 @@
 endef
 
 # Builds the library that Mojo services must be linked with.
-$(MOJO_SHARED_LIB): | mojo-env-check
+$(MOJO_SHARED_LIB): $(MOJO_BUILD_DIR)/obj/mojo/public/platform/native/system.system_thunks.o | mojo-env-check
 	mkdir -p $(dir $@)
 	ar rcs $@ $(MOJO_BUILD_DIR)/obj/mojo/public/platform/native/system.system_thunks.o