diff --git a/action.yml b/action.yml
index be9503d..7faedbc 100644
--- a/action.yml
+++ b/action.yml
@@ -125,8 +125,9 @@ runs:
         chmod ugoa+rw -R '${{ github.workspace }}' '${{ github.action_path }}'
 
         # Write out customizations via env vars to avoid heredoc injection
-        printf '%s' "$INPUT_CSS" > '${{ github.action_path }}/custom.css'
-        printf '%s' "$INPUT_CUSTOMIZATIONS" > '${{ github.action_path }}/custom.yaml'
+        # Only create files when inputs are non-empty; empty files cause addStyleTag/readYamlFile to fail
+        [ -n "$INPUT_CSS" ] && printf '%s' "$INPUT_CSS" > '${{ github.action_path }}/custom.css' || true
+        [ -n "$INPUT_CUSTOMIZATIONS" ] && printf '%s' "$INPUT_CUSTOMIZATIONS" > '${{ github.action_path }}/custom.yaml' || true
 
         # Prepare inputs that should be passed to the docker container.
         cat <<'__EOF__' >docker.env