diff --git a/.circleci/config.yml b/.circleci/config.yml
index 665efed..59fa2fa 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -74,20 +74,6 @@ jobs:
       - setup_ubuntu:
           OTP_VERSION: "23.3.4.18"
       - run_build
-  macos_1106_otp21:
-    executor: macos_1106
-    steps:
-      - checkout
-      - setup_macos:
-          OTP_VERSION: "21"
-      - run_build
-  macos_1106_otp22:
-    executor: macos_1106
-    steps:
-      - checkout
-      - setup_macos:
-          OTP_VERSION: "22"
-      - run_build
   macos_1106_otp23:
     executor: macos_1106
     steps:
@@ -102,6 +88,4 @@ workflows:
       - ubuntu_2004_otp21
       - ubuntu_2004_otp22
       - ubuntu_2004_otp23
-      - macos_1106_otp21
-      - macos_1106_otp22
       - macos_1106_otp23
diff --git a/Makefile b/Makefile
index f9e1fa2..016b3c3 100644
--- a/Makefile
+++ b/Makefile
@@ -1,12 +1,13 @@
-REBAR=rebar3
+REBAR3 ?= $(shell test -e `which rebar3` 2>/dev/null && which rebar3 || echo "./rebar3")
 
 all: compile
 
 compile:
-	${REBAR} compile
+	${REBAR3} compile
 
 clean:
-	${REBAR} clean
+	${REBAR3} clean
+	@rm -fr c_src/secp256k1
 
 test: compile
-	${REBAR} eunit
\ No newline at end of file
+	${REBAR3} eunit
\ No newline at end of file
diff --git a/rebar3 b/rebar3
new file mode 100755
index 0000000..13db1ce
Binary files /dev/null and b/rebar3 differ