diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9b8be55..022caf7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: 1.67.0
           override: true
 
       # Install for Anvil
@@ -48,7 +48,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: 1.67.0
           override: true
           components: rustfmt, clippy
       - name: cargo fmt
diff --git a/README.md b/README.md
index ec7cfa4..7841cc0 100644
--- a/README.md
+++ b/README.md
@@ -65,6 +65,10 @@ Tests require the following installed:
 - [x] Proof generations and verification using Arkworks
 - [ ] CLI for common operations
 
+## Known limitations
+
+Currently, due to an issue in our upstream (https://github.com/wasmerio/wasmer/issues/4072), this crate works as expected only up to Rust version `1.67.0`; in newer Rust versions, `wasmer` is currently unsound.
+
 ## Acknowledgements
 
 This library would not have been possibly without the great work done in:
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..74cb24a
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,3 @@
+[toolchain]
+channel = "stable"
+version = "1.67.0"
\ No newline at end of file