diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 9ca603c5..33bb4b6f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -55,13 +55,14 @@ jobs:
       if: matrix.build == 'stable' 
 
   rustfmt:
-    name: Rustfmt
+    name: Rustfmt & Docs
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
     - name: Install Rust
       run: rustup update stable && rustup default stable && rustup component add rustfmt
     - run: cargo fmt -- --check
+    - run: cargo doc --all-features
 
   wasm:
     name: WebAssembly
diff --git a/Cargo.toml b/Cargo.toml
index 66cf59e5..83371fe8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "flate2"
 authors = ["Alex Crichton <alex@alexcrichton.com>", "Josh Triplett <josh@joshtriplett.org>"]
-version = "1.0.29"
+version = "1.0.30"
 edition = "2018"
 license = "MIT OR Apache-2.0"
 readme = "README.md"
diff --git a/src/ffi/c.rs b/src/ffi/c.rs
index 75d69b14..0c3e4e8e 100644
--- a/src/ffi/c.rs
+++ b/src/ffi/c.rs
@@ -403,7 +403,7 @@ mod c_backend {
     #[cfg(feature = "zlib-ng")]
     use libz_ng_sys as libz;
 
-    #[cfg(feature = "zlib-rs")]
+    #[cfg(all(not(feature = "zlib-ng"), feature = "zlib-rs"))]
     use libz_rs_sys as libz;
 
     #[cfg(all(not(feature = "zlib-ng"), feature = "cloudflare_zlib"))]
@@ -443,7 +443,7 @@ mod c_backend {
 
     #[cfg(feature = "zlib-ng")]
     const ZLIB_VERSION: &'static str = "2.1.0.devel\0";
-    #[cfg(feature = "zlib-rs")]
+    #[cfg(all(not(feature = "zlib-ng"), feature = "zlib-rs"))]
     const ZLIB_VERSION: &'static str = "0.1.0\0";
     #[cfg(not(any(feature = "zlib-ng", feature = "zlib-rs")))]
     const ZLIB_VERSION: &'static str = "1.2.8\0";