diff --git a/build.sh b/build.sh
index 33db8d4..4c2e347 100755
--- a/build.sh
+++ b/build.sh
@@ -10,9 +10,9 @@ if [ "$(uname)" = "Darwin" ]; then
     echo ""
     echo "This build script is using Docker container runtime to run the build in an isolated environment."
     echo ""
-    docker run --rm -it -v $(pwd):/antora $image $cmd
+    docker run --rm -it -v "$(pwd):/antora" $image $cmd
 
-elif [ "$(expr substr $(uname -s) 1 5)" = "Linux" ]; then
+elif [ "$(expr substr "$(uname -s)" 1 5)" = "Linux" ]; then
     # Running on Linux.
     # Check whether podman is available, else faill back to docker
     # which requires root.
@@ -21,7 +21,7 @@ elif [ "$(expr substr $(uname -s) 1 5)" = "Linux" ]; then
         echo ""
         echo "This build script is using Podman to run the build in an isolated environment."
         echo ""
-	podman run --rm -it -v $(pwd):/antora:z $image $cmd
+	podman run --rm -it -v "$(pwd):/antora:z" $image $cmd
 
     elif [ -f /usr/bin/docker ]; then
         echo ""
@@ -29,13 +29,13 @@ elif [ "$(expr substr $(uname -s) 1 5)" = "Linux" ]; then
         echo ""
 
         if groups | grep -wq "docker"; then
-	    docker run --rm -it -v $(pwd):/antora:z $image $cmd
+	    docker run --rm -it -v "$(pwd):/antora:z" $image $cmd
 	else
             echo ""
             echo "This build script is using $runtime to run the build in an isolated environment. You might be asked for your password."
             echo "You can avoid this by adding your user to the 'docker' group, but be aware of the security implications. See https://docs.docker.com/install/linux/linux-postinstall/."
             echo ""
-            sudo docker run --rm -it -v $(pwd):/antora:z $image $cmd
+            sudo docker run --rm -it -v "$(pwd):/antora:z" $image $cmd
 	fi
     else
         echo ""
diff --git a/preview.sh b/preview.sh
index 5b4a8ed..4270107 100755
--- a/preview.sh
+++ b/preview.sh
@@ -5,9 +5,9 @@ if [ "$(uname)" = "Darwin" ]; then
     # Let's assume that the user has the Docker CE installed
     # which doesn't require a root password.
     echo "The preview will be available at http://localhost:8080/"
-    docker run --rm -v $(pwd):/antora:ro -v $(pwd)/nginx.conf:/etc/nginx/conf.d/default.conf:ro -p 8080:80 nginx
+    docker run --rm -v "$(pwd):/antora:ro" -v "$(pwd)/nginx.conf:/etc/nginx/conf.d/default.conf:ro" -p 8080:80 nginx
 
-elif [ "$(expr substr $(uname -s) 1 5)" = "Linux" ]; then
+elif [ "$(expr substr "$(uname -s)" 1 5)" = "Linux" ]; then
     # Running on Linux.
     # Fedora Workstation has python3 installed as a default, so using that
     echo ""