diff --git a/Cargo.lock b/Cargo.lock
index fed2bf6f..3623d3d3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1990,7 +1990,7 @@ dependencies = [
 
 [[package]]
 name = "quickjs-wasm-sys"
-version = "1.0.0"
+version = "1.1.0-alpha.1"
 dependencies = [
  "anyhow",
  "bindgen",
diff --git a/Makefile b/Makefile
index 424bd05d..60180c4c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,6 @@
 .PHONY: cli core test fmt clean
 .DEFAULT_GOAL := cli
 
-download-wasi-sdk:
-	./install-wasi-sdk.sh
-
 install:
 	cargo install --path crates/cli
 
diff --git a/crates/quickjs-wasm-rs/Cargo.toml b/crates/quickjs-wasm-rs/Cargo.toml
index 1151de46..826fa58e 100644
--- a/crates/quickjs-wasm-rs/Cargo.toml
+++ b/crates/quickjs-wasm-rs/Cargo.toml
@@ -11,7 +11,7 @@ categories = ["api-bindings"]
 
 [dependencies]
 anyhow = { workspace = true }
-quickjs-wasm-sys = { version = "1.0.0", path = "../quickjs-wasm-sys" }
+quickjs-wasm-sys = { version = "1.1.0-alpha.1", path = "../quickjs-wasm-sys" }
 serde = { version = "1.0", features = ["derive"] }
 once_cell = "1.16"
 
diff --git a/crates/quickjs-wasm-sys/CHANGELOG.md b/crates/quickjs-wasm-sys/CHANGELOG.md
index 285d8f15..e9d916a5 100644
--- a/crates/quickjs-wasm-sys/CHANGELOG.md
+++ b/crates/quickjs-wasm-sys/CHANGELOG.md
@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- Added: `QUICKJS_WASM_SYS_WASI_SDK_MAJOR_VERSION` and `QUICKJS_WASM_SYS_WASI_SDK_MINOR_VERSION` build-time environment variables to control which version of the WASI SDK to use.
+- Fixed: Changing the `QUICKJS_WASM_SYS_WASI_SDK_PATH` build time environment variable will trigger a rebuild of the crate.
+
 ## 1.0.0 - 2023-05-16
 
 No changes from 0.1.2. Just updating version to show we're confident in the existing bindings.
diff --git a/crates/quickjs-wasm-sys/Cargo.toml b/crates/quickjs-wasm-sys/Cargo.toml
index 11c6d1ab..be211247 100644
--- a/crates/quickjs-wasm-sys/Cargo.toml
+++ b/crates/quickjs-wasm-sys/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "quickjs-wasm-sys"
-version = "1.0.0"
+version = "1.1.0-alpha.1"
 authors.workspace = true
 edition.workspace = true 
 license.workspace = true
diff --git a/crates/quickjs-wasm-sys/README.md b/crates/quickjs-wasm-sys/README.md
index ee82fc69..5c17ca47 100644
--- a/crates/quickjs-wasm-sys/README.md
+++ b/crates/quickjs-wasm-sys/README.md
@@ -8,4 +8,4 @@ To publish this crate to crates.io, run `./publish.sh`.
 
 ## Using a custom WASI SDK
 
-This crate can be compiled using a custom [WASI SDK](https://github.com/WebAssembly/wasi-sdk). When building this crate, set the `QUICKJS_WASM_SYS_WASI_SDK_PATH` environment variable to the absolute path where you installed the SDK.
+This crate can be compiled using a custom [WASI SDK](https://github.com/WebAssembly/wasi-sdk). When building this crate, set the `QUICKJS_WASM_SYS_WASI_SDK_PATH` environment variable to the absolute path where you installed the SDK. You can also use a particular version of the WASI SDK by setting the `QUICKJS_WASM_SYS_WASI_SDK_MAJOR_VERSION` and `QUICKJS_WASM_SYS_WASI_SDK_MINOR_VERSION` environment variables to the appropriate versions.
diff --git a/crates/quickjs-wasm-sys/build.rs b/crates/quickjs-wasm-sys/build.rs
index b562d5d9..68f5c8c4 100644
--- a/crates/quickjs-wasm-sys/build.rs
+++ b/crates/quickjs-wasm-sys/build.rs
@@ -70,8 +70,17 @@ async fn download_wasi_sdk() -> Result<PathBuf> {
 
     fs::create_dir_all(&wasi_sdk_dir)?;
 
+    const MAJOR_VERSION_ENV_VAR: &str = "QUICKJS_WASM_SYS_WASI_SDK_MAJOR_VERSION";
+    const MINOR_VERSION_ENV_VAR: &str = "QUICKJS_WASM_SYS_WASI_SDK_MINOR_VERSION";
+    println!("cargo:rerun-if-env-changed={MAJOR_VERSION_ENV_VAR}");
+    println!("cargo:rerun-if-env-changed={MINOR_VERSION_ENV_VAR}");
+    let major_version =
+        env::var(MAJOR_VERSION_ENV_VAR).unwrap_or(WASI_SDK_VERSION_MAJOR.to_string());
+    let minor_version =
+        env::var(MINOR_VERSION_ENV_VAR).unwrap_or(WASI_SDK_VERSION_MINOR.to_string());
+
     let mut archive_path = wasi_sdk_dir.clone();
-    archive_path.push("wasi-sdk.tar.gz");
+    archive_path.push(format!("wasi-sdk-{major_version}-{minor_version}.tar.gz"));
 
     // Download archive if necessary
     if !archive_path.try_exists()? {
@@ -83,8 +92,7 @@ async fn download_wasi_sdk() -> Result<PathBuf> {
             other => return Err(anyhow!("Unsupported platform tuple {:?}", other)),
         };
 
-        // FIXME: Make this HTTPS!
-        let uri = format!("https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-{}/wasi-sdk-{}.{}-{}.tar.gz", WASI_SDK_VERSION_MAJOR, WASI_SDK_VERSION_MAJOR, WASI_SDK_VERSION_MINOR, file_suffix);
+        let uri = format!("https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-{major_version}/wasi-sdk-{major_version}.{minor_version}-{file_suffix}.tar.gz");
         let mut body = get_uri(uri).await?;
         let mut archive = fs::File::create(&archive_path)?;
         while let Some(frame) = body.frame().await {
@@ -122,7 +130,9 @@ async fn download_wasi_sdk() -> Result<PathBuf> {
 }
 
 async fn get_wasi_sdk_path() -> Result<PathBuf> {
-    if let Ok(path) = env::var("QUICKJS_WASM_SYS_WASI_SDK_PATH") {
+    const WASI_SDK_PATH_ENV_VAR: &str = "QUICKJS_WASM_SYS_WASI_SDK_PATH";
+    println!("cargo:rerun-if-env-changed={WASI_SDK_PATH_ENV_VAR}");
+    if let Ok(path) = env::var(WASI_SDK_PATH_ENV_VAR) {
         return Ok(path.into());
     }
     download_wasi_sdk().await
diff --git a/install-wasi-sdk.sh b/install-wasi-sdk.sh
deleted file mode 100755
index 4b11f7b7..00000000
--- a/install-wasi-sdk.sh
+++ /dev/null
@@ -1,34 +0,0 @@
-#!/usr/bin/env bash
-
-set -euo pipefail
-
-if [[ "$(basename $(pwd))" != "javy" ]]; then
-    echo "Run this inside in the root of the javy repo" 1>&2
-    exit 1
-fi
-
-# Don't try and install the wasi-sdk if the user has specified the wasi-sdk is installed elsewhere
-set +u
-if [[ -n "$QUICKJS_WASM_SYS_WASI_SDK_PATH" ]]; then
-    # Check that something is present where the user says the wasi-sdk is located
-    if [[ ! -d "$QUICKJS_WASM_SYS_WASI_SDK_PATH" ]]; then
-        echo "Download the wasi-sdk to $QUICKJS_WASM_SYS_WASI_SDK_PATH" 1>&2
-        exit 1
-    fi
-    exit 0
-fi
-set -u
-
-PATH_TO_SDK="crates/quickjs-wasm-sys/wasi-sdk"
-if [[ ! -d $PATH_TO_SDK ]]; then
-    TMPGZ=$(mktemp)
-    VERSION_MAJOR="20"
-    VERSION_MINOR="0"
-    if [[ "$(uname -s)" == "Darwin" ]]; then
-        curl --fail --location --silent https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-${VERSION_MAJOR}/wasi-sdk-${VERSION_MAJOR}.${VERSION_MINOR}-macos.tar.gz --output $TMPGZ
-    else
-        curl --fail --location --silent https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-${VERSION_MAJOR}/wasi-sdk-${VERSION_MAJOR}.${VERSION_MINOR}-linux.tar.gz --output $TMPGZ
-    fi
-    mkdir $PATH_TO_SDK
-    tar xf $TMPGZ -C $PATH_TO_SDK --strip-components=1
-fi