diff --git a/.github/workflows/build-and-upload-binaries-ci.yml b/.github/workflows/build-and-upload-binaries-ci.yml
index 26f3ccb588c..535a07e2214 100644
--- a/.github/workflows/build-and-upload-binaries-ci.yml
+++ b/.github/workflows/build-and-upload-binaries-ci.yml
@@ -63,7 +63,7 @@ jobs:
       - name: Install Rust stable
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.69.0
+          toolchain: stable
 
       - name: Build all binaries
         uses: actions-rs/cargo@v1
@@ -74,7 +74,7 @@ jobs:
       - name: Install Rust stable
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.69.0
+          toolchain: stable
           target: wasm32-unknown-unknown
           override: true
           components: rustfmt, clippy
diff --git a/.github/workflows/contracts-build.yml b/.github/workflows/contracts-build.yml
index bc7a343cb41..36d9fab4e32 100644
--- a/.github/workflows/contracts-build.yml
+++ b/.github/workflows/contracts-build.yml
@@ -14,7 +14,7 @@ jobs:
       - name: Install Rust stable
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.69.0
+          toolchain: stable
           target: wasm32-unknown-unknown
           override: true
           components: rustfmt, clippy
diff --git a/Makefile b/Makefile
index c74994904ed..3fb89513402 100644
--- a/Makefile
+++ b/Makefile
@@ -172,10 +172,10 @@ contracts-wasm-build:
 	RUSTFLAGS='-C link-arg=-s' cargo build --lib --manifest-path contracts/Cargo.toml --release --target wasm32-unknown-unknown
 
 contracts-wasm-opt:
-	wasm-opt --disable-sign-ext -Os $(VESTING_CONTRACT) -o $(VESTING_CONTRACT)
-	wasm-opt --disable-sign-ext -Os $(MIXNET_CONTRACT) -o $(MIXNET_CONTRACT)
-	wasm-opt --disable-sign-ext -Os $(SERVICE_PROVIDER_DIRECTORY_CONTRACT) -o $(SERVICE_PROVIDER_DIRECTORY_CONTRACT)
-	wasm-opt --disable-sign-ext -Os $(NAME_SERVICE_CONTRACT) -o $(NAME_SERVICE_CONTRACT)
+	wasm-opt --signext-lowering -Os $(VESTING_CONTRACT) -o $(VESTING_CONTRACT)
+	wasm-opt --signext-lowering -Os $(MIXNET_CONTRACT) -o $(MIXNET_CONTRACT)
+	wasm-opt --signext-lowering -Os $(SERVICE_PROVIDER_DIRECTORY_CONTRACT) -o $(SERVICE_PROVIDER_DIRECTORY_CONTRACT)
+	wasm-opt --signext-lowering -Os $(NAME_SERVICE_CONTRACT) -o $(NAME_SERVICE_CONTRACT)
 
 contract-schema:
 	$(MAKE) -C contracts schema
diff --git a/contracts/mixnet/Makefile b/contracts/mixnet/Makefile
index 01452be7010..4583495c9a9 100644
--- a/contracts/mixnet/Makefile
+++ b/contracts/mixnet/Makefile
@@ -1,5 +1,5 @@
 opt: wasm
-	wasm-opt --disable-sign-ext -Os ../target/wasm32-unknown-unknown/release/mixnet_contract.wasm -o ../target/wasm32-unknown-unknown/release/mixnet_contract.wasm
+	wasm-opt --signext-lowering -Os ../target/wasm32-unknown-unknown/release/mixnet_contract.wasm -o ../target/wasm32-unknown-unknown/release/mixnet_contract.wasm
 
 wasm:
 	RUSTFLAGS='-C link-arg=-s' cargo build --release --target wasm32-unknown-unknown