diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 439a18d..d4090f6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -197,7 +197,6 @@
 
 * `tests/expectations/tests/libclang-9/my_test.rs`
 * `tests/expectations/tests/libclang-5/my_test.rs`
-* `tests/expectations/tests/libclang-4/my_test.rs`
 
 If you need to update the test expectations for a test file that generates
 different bindings for different `libclang` versions, you *don't* need to have
diff --git a/book/src/requirements.md b/book/src/requirements.md
index 8a7cbcb..7cce87a 100644
--- a/book/src/requirements.md
+++ b/book/src/requirements.md
@@ -7,13 +7,9 @@
 `bindgen` leverages `libclang` to preprocess, parse, and type check C and C++
 header files.
 
-It is recommended to use Clang 4.0 or greater, however `bindgen` can run with
-older Clangs with some features disabled.
+It is required to use Clang 5.0 or greater.
 
-* **If you are generating bindings to C++,** you almost definitely want 4.0 or
-greater.
-
-### Installing Clang 4.0
+### Installing Clang
 
 #### Windows
 
@@ -50,9 +46,7 @@
 # apt install llvm-dev libclang-dev clang
 ```
 
-Ubuntu 18.04 provides the necessary packages directly. If you are using older
-version of Ubuntu or other Debian-based distros, you may need to add the LLVM
-repos to get version 4.0. See http://apt.llvm.org/.
+Ubuntu 18.04 provides the necessary packages directly.
 
 #### Arch
 
@@ -76,7 +70,7 @@
 
 #### From source
 
-If your package manager doesn't yet offer Clang 4.0, you'll need to build from
+If your package manager doesn't yet offer Clang 5.0, you'll need to build from
 source. For that, follow the
 instructions [here](http://clang.llvm.org/get_started.html).