diff --git a/action.yml b/action.yml
index 8cc5a32..4caa0df 100644
--- a/action.yml
+++ b/action.yml
@@ -170,7 +170,7 @@ runs:
         if [ "${{ inputs.trust-runner-user }}" == "true" ]; then
           echo "trusted-users = root $USER" >> ${NIX_EXTRA_CONF_FILE}
         fi
-        if [ -n "$NIX_EXTRA_CONF" ]; then
+        if [ -n "$NIX_EXTRA_CONF_FILE" ]; then
           export NIX_INSTALLER_EXTRA_CONF=$(cat ${NIX_EXTRA_CONF_FILE})
           echo "Set NIX_INSTALLER_EXTRA_CONF=$NIX_INSTALLER_EXTRA_CONF"
         fi