diff --git a/build.sh b/build.sh
index cbb0292..4c8339a 100644
--- a/build.sh
+++ b/build.sh
@@ -14,13 +14,16 @@ get_yaml_array() {
 }
 export -f get_yaml_array # this makes the function available to all modules
 
-# Automatically determine which Fedora version we're building.
-export FEDORA_VERSION="$(grep -Po '(?<=VERSION_ID=)\d+' /usr/lib/os-release)"
+# Declare dynamically generated variables as read-only and exported
+declare -rx IMAGE_NAME BASE_IMAGE FEDORA_VERSION
 
 # Read configuration variables.
 BASE_IMAGE="$(yq '.base-image' "$RECIPE_FILE")"
 IMAGE_NAME="$(yq '.name' "$RECIPE_FILE")"
 
+# Automatically determine which Fedora version we're building.
+FEDORA_VERSION="$(grep -Po '(?<=VERSION_ID=)\d+' /usr/lib/os-release)"
+
 # Welcome.
 echo "Building $IMAGE_NAME from Fedora $FEDORA_VERSION ($BASE_IMAGE)."