diff --git a/.gitignore b/.gitignore
index eab4c2612..344aa1379 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,4 +16,5 @@ dist/sequenceTest.html
 
 .vscode/
 cypress/platform/current.html
-cypress/platform/experimental.html
\ No newline at end of file
+cypress/platform/experimental.html
+local/
\ No newline at end of file
diff --git a/src/mermaidAPI.js b/src/mermaidAPI.js
index 1d15b8f5f..7ff1511d4 100644
--- a/src/mermaidAPI.js
+++ b/src/mermaidAPI.js
@@ -539,6 +539,8 @@ function initialize(options) {
   if (options.theme && themes[options.theme]) {
     // Todo merge with user options
     options.themeVariables = themes[options.theme];
+  } else {
+    options.themeVariables = themes.default;
   }
 
   const config = typeof options === 'object' ? setSiteConfig(options) : getSiteConfig();