diff --git a/.circleci/config.yml b/.circleci/config.yml
index 8007b279b..2e682aa29 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -23,7 +23,7 @@ jobs:
           command: cargo generate-lockfile
       - restore_cache:
           keys:
-            - v4-cargo-cache-{{ arch }}-{{ checksum "Cargo.lock" }}
+            - cargo-cache-{{ .Environment.CACHE_VERSION }}-{{ arch }}-{{ checksum "Cargo.lock" }}
       - run:
           name: Build
           command: WITH_LIBSNARK=1 RUSTFLAGS="-D warnings" ./build.sh
@@ -33,7 +33,7 @@ jobs:
             - target/debug/.fingerprint
             - target/debug/build
             - target/debug/deps
-          key: v4-cargo-cache-{{ arch }}-{{ checksum "Cargo.lock" }}
+          key: cargo-cache-{{ .Environment.CACHE_VERSION }}-{{ arch }}-{{ checksum "Cargo.lock" }}
   test:
     docker:
       - image: zokrates/env:latest
@@ -48,7 +48,7 @@ jobs:
           command: cargo generate-lockfile
       - restore_cache:
           keys:
-            - v4-cargo-cache-{{ arch }}-{{ checksum "Cargo.lock" }}
+            - cargo-cache-{{ .Environment.CACHE_VERSION }}-{{ arch }}-{{ checksum "Cargo.lock" }}
       - run:
           name: Check format
           command: cargo fmt --all -- --check
@@ -82,7 +82,7 @@ jobs:
           command: cargo generate-lockfile
       - restore_cache:
           keys:
-            - v4-cargo-cache-{{ arch }}-{{ checksum "Cargo.lock" }}
+            - cargo-cache-{{ .Environment.CACHE_VERSION }}-{{ arch }}-{{ checksum "Cargo.lock" }}
       - run:
           name: Test on firefox
           command: |
@@ -103,7 +103,7 @@ jobs:
           command: cargo generate-lockfile
       - restore_cache:
           keys:
-            - v4-cargo-cache-{{ arch }}-{{ checksum "Cargo.lock" }}
+            - cargo-cache-{{ .Environment.CACHE_VERSION }}-{{ arch }}-{{ checksum "Cargo.lock" }}
       - run:
           name: Run integration tests
           no_output_timeout: "30m"
diff --git a/Cargo.lock b/Cargo.lock
index b46577108..1afa62d6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1121,9 +1121,9 @@ checksum = "f0a01e0497841a3b2db4f8afa483cce65f7e96a3498bd6c541734792aeac8fe7"
 
 [[package]]
 name = "git2"
-version = "0.13.23"
+version = "0.13.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2a8057932925d3a9d9e4434ea016570d37420ddb1ceed45a174d577f24ed6700"
+checksum = "f29229cc1b24c0e6062f6e742aa3e256492a5323365e5ed3413599f8a5eff7d6"
 dependencies = [
  "bitflags",
  "libc",
@@ -1246,9 +1246,9 @@ checksum = "7b2f96d100e1cf1929e7719b7edb3b90ab5298072638fccd77be9ce942ecdfce"
 
 [[package]]
 name = "libgit2-sys"
-version = "0.12.24+1.3.0"
+version = "0.12.26+1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ddbd6021eef06fb289a8f54b3c2acfdd85ff2a585dfbb24b8576325373d2152c"
+checksum = "19e1c899248e606fbfe68dcb31d8b0176ebab833b103824af31bddf4b7457494"
 dependencies = [
  "cc",
  "libc",
diff --git a/zokrates_core/Cargo.toml b/zokrates_core/Cargo.toml
index 194b9b21a..07184a7ea 100644
--- a/zokrates_core/Cargo.toml
+++ b/zokrates_core/Cargo.toml
@@ -66,4 +66,4 @@ zokrates_fs_resolver = { version = "0.5", path = "../zokrates_fs_resolver"}
 [build-dependencies]
 cc = { version = "1.0", features = ["parallel"], optional = true }
 cmake = { version = "=0.1.45", optional = true }
-git2 = { version = "0.13.1", optional = true }
+git2 = { version = "0.13.25", optional = true }
diff --git a/zokrates_core/build.rs b/zokrates_core/build.rs
index 4c8e53795..8d281b522 100644
--- a/zokrates_core/build.rs
+++ b/zokrates_core/build.rs
@@ -8,7 +8,7 @@ extern crate git2;
 fn main() {
     #[cfg(feature = "libsnark")]
     {
-        use git2::{Oid, Repository, ResetType};
+        use git2::Repository;
         use std::env;
         use std::fs::remove_dir;
         use std::path::PathBuf;
@@ -25,11 +25,17 @@ fn main() {
             Repository::clone(LIBSNARK_URL, libsnark_source_path).unwrap()
         });
 
-        let commit = Oid::from_str(LIBSNARK_COMMIT).unwrap();
-        let commit = repo.find_commit(commit).unwrap();
+        // Unencrypted `git://` protocol is no longer supported on GitHub
+        // so we replace all submodule urls to use `https://`
+        let gitmodules_path = libsnark_source_path.join(".gitmodules");
+        let gitmodules = std::fs::read_to_string(&gitmodules_path)
+            .unwrap()
+            .replace("git://", "https://");
 
-        repo.reset(&commit.as_object(), ResetType::Hard, None)
-            .unwrap();
+        std::fs::write(&gitmodules_path, gitmodules).unwrap();
+
+        let object = repo.revparse_single(LIBSNARK_COMMIT).unwrap();
+        repo.checkout_tree(&object, None).unwrap();
 
         for mut s in repo.submodules().unwrap() {
             s.update(true, None).unwrap();