diff --git a/.github/workflows/continous-integration-os.patch.yml b/.github/workflows/continous-integration-os.patch.yml
index 8f9018b52..d3bb7733b 100644
--- a/.github/workflows/continous-integration-os.patch.yml
+++ b/.github/workflows/continous-integration-os.patch.yml
@@ -21,7 +21,7 @@ jobs:
       matrix:
         # TODO: Windows was removed for now, see https://github.com/ZcashFoundation/zebra/issues/3801
         os: [ubuntu-latest, macos-latest]
-        rust: [stable, beta]
+        rust: [1.63, beta]
         exclude:
           - os: macos-latest
             rust: beta
diff --git a/.github/workflows/continous-integration-os.yml b/.github/workflows/continous-integration-os.yml
index cc275fdd7..1fb35ff03 100644
--- a/.github/workflows/continous-integration-os.yml
+++ b/.github/workflows/continous-integration-os.yml
@@ -64,7 +64,8 @@ jobs:
       matrix:
         # TODO: Windows was removed for now, see https://github.com/ZcashFoundation/zebra/issues/3801
         os: [ubuntu-latest, macos-latest]
-        rust: [stable, beta]
+        # Rust 1.64 hangs when downloading the Zcash Parameters on GitHub Actions runners
+        rust: [1.63, beta]
         exclude:
         # TODO: re-enable beta Rust tests on ubuntu (#4929)
           - os: ubuntu-latest
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 9fc690558..f957c4f44 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -61,7 +61,8 @@ jobs:
 
       - uses: actions-rs/toolchain@v1.0.7
         with:
-          toolchain: stable
+          # Rust 1.64 hangs when downloading the Zcash Parameters on GitHub Actions runners
+          toolchain: 1.63
           override: true
           profile: minimal
           components: llvm-tools-preview
diff --git a/book/src/user/supported-platforms.md b/book/src/user/supported-platforms.md
index c51e621cb..4724e9630 100644
--- a/book/src/user/supported-platforms.md
+++ b/book/src/user/supported-platforms.md
@@ -15,6 +15,15 @@ ensures that each tier 1 platform builds and passes tests after each change.
 
 For the full requirements, see [Tier 1 platform policy](platform-tier-policy.md#tier-1-platform-policy) in the Platform Tier Policy.
 
+| platform | os | notes | rust | artifacts
+| -------|-------|-------|-------|-------
+| `x86_64-unknown-linux-gnu` | [Debian 11](https://www.debian.org/releases/bullseye/) | 64-bit | [1.63](https://github.com/rust-lang/rust/releases) | Docker
+
+### Temporarily Unsupported
+
+Zcash parameter downloads currently [hang when built with Rust 1.64 and later](https://github.com/ZcashFoundation/zebra/issues/5091).
+Those Rust versions are unsupported until that bug is fixed.
+
 | platform | os | notes | rust | artifacts
 | -------|-------|-------|-------|-------
 | `x86_64-unknown-linux-gnu` | [Debian 11](https://www.debian.org/releases/bullseye/) | 64-bit | [latest stable release](https://github.com/rust-lang/rust/releases) | Docker
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 16281827d..62f4d8400 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -7,7 +7,7 @@
 # - runtime: is our runtime environment
 #
 # This stage implements cargo-chef for docker layer caching
-FROM rust:bullseye as chef
+FROM rust:1.63-bullseye as chef
 RUN cargo install cargo-chef --locked
 WORKDIR /opt/zebrad
 
diff --git a/docker/zcash-params/Dockerfile b/docker/zcash-params/Dockerfile
index 1036a2be4..70a858c69 100644
--- a/docker/zcash-params/Dockerfile
+++ b/docker/zcash-params/Dockerfile
@@ -1,6 +1,6 @@
 # This steps implement cargo-chef for docker layer caching
 # This image is for caching Zcash Sprout and Sapling parameters
-FROM rust:bullseye as chef
+FROM rust:1.63-bullseye as chef
 RUN cargo install cargo-chef --locked
 WORKDIR /opt/zebrad