diff --git a/c_src/Makefile b/c_src/Makefile
index df72bd5..968165f 100644
--- a/c_src/Makefile
+++ b/c_src/Makefile
@@ -5,9 +5,9 @@ BASEDIR := $(abspath $(CURDIR)/..)
 
 PROJECT = xxhash
 
-ERTS_INCLUDE_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s/erts-~s/include/\", [code:root_dir(), erlang:system_info(version)]).")
-ERL_INTERFACE_INCLUDE_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s\", [code:lib_dir(erl_interface, include)]).")
-ERL_INTERFACE_LIB_DIR ?= $(shell erl -noshell -s init stop -eval "io:format(\"~s\", [code:lib_dir(erl_interface, lib)]).")
+ERTS_INCLUDE_DIR ?= $(shell erl -noshell -eval "io:format(\"~s/erts-~s/include/\", [code:root_dir(), erlang:system_info(version)])." -s init stop)
+ERL_INTERFACE_INCLUDE_DIR ?= $(shell erl -noshell -eval "io:format(\"~s\", [code:lib_dir(erl_interface, include)])." -s init stop)
+ERL_INTERFACE_LIB_DIR ?= $(shell erl -noshell -eval "io:format(\"~s\", [code:lib_dir(erl_interface, lib)])." -s init stop)
 
 C_SRC_DIR = $(CURDIR)
 C_SRC_OUTPUT ?= $(CURDIR)/../priv/$(PROJECT).so