diff --git a/setup-toolchain.sh b/setup-toolchain.sh
index f8d764b613271..c1c8366bf5e76 100755
--- a/setup-toolchain.sh
+++ b/setup-toolchain.sh
@@ -1,9 +1,12 @@
 #!/bin/bash
 # Set up the appropriate rustc toolchain
 
-cd $(dirname $0)
+cd "$(dirname "$0")"
+
+if ! command -v rustup-toolchain-install-master > /dev/null; then
+  cargo install rustup-toolchain-install-master --debug
+fi
 
-cargo install rustup-toolchain-install-master --debug || echo "rustup-toolchain-install-master already installed"
 RUSTC_HASH=$(git ls-remote https://github.com/rust-lang/rust.git master | awk '{print $1}')
-rustup-toolchain-install-master -f -n master $RUSTC_HASH
+rustup-toolchain-install-master -f -n master "$RUSTC_HASH"
 rustup override set master