diff --git a/_extensions/diagram/diagram.lua b/_extensions/diagram/diagram.lua
index c2e8879..6ca4b0d 100644
--- a/_extensions/diagram/diagram.lua
+++ b/_extensions/diagram/diagram.lua
@@ -155,12 +155,27 @@ local mermaid = {
       return with_working_directory(tmpdir, function ()
         local infile = 'diagram.mmd'
         local outfile = 'diagram.' .. file_extension
+        local args = {"--pdfFit", "--input", infile, "--output", outfile}
+        if self.opt then
+          if self.opt.theme then
+            table.insert(args, '--theme' .. stringify(self.opt.theme))
+            table.insert(args, stringify(self.opt.cssFile))
+          end
+          if self.opt.configFile then
+            table.insert(args, '--configFile')
+            table.insert(args, stringify(self.opt.configFile))
+          end
+          if self.opt.cssFile then
+            table.insert(args, '--cssFile' .. stringify(self.opt.cssFile))
+            table.insert(args, stringify(self.opt.cssFile))
+          end
+          if self.opt.puppeteerConfigFile then
+            table.insert(args, '--puppeteerConfigFile')
+            table.insert(args, stringify(self.opt.puppeteerConfigFile))
+          end
+        end
         write_file(infile, code)
-        pipe(
-          self.execpath or 'mmdc',
-          {"--pdfFit", "--input", infile, "--output", outfile},
-          ''
-        )
+        pipe(self.execpath or 'mmdc', args,'')
         return read_file(outfile), mime_type
       end)
     end)
diff --git a/test/input-mermaid.md b/test/input-mermaid.md
index c16c16d..073eef8 100644
--- a/test/input-mermaid.md
+++ b/test/input-mermaid.md
@@ -5,6 +5,19 @@ Mermaid is a JavaScript-based diagramming and charting tool.
 ``` mermaid
 %%| filename: flowchart
 %%| fig-cap: A simple flowchart.
+%%{
+  init: {
+    'theme': 'base',
+    'themeVariables': {
+      'primaryColor': '#BB2528',
+      'primaryTextColor': '#fff',
+      'primaryBorderColor': '#7C0000',
+      'lineColor': '#F8B229',
+      'secondaryColor': '#006100',
+      'tertiaryColor': '#fff'
+    }
+  }
+}%%
 graph TD;
     A-->B;
     A-->C;
diff --git a/test/test-mermaid.yaml b/test/test-mermaid.yaml
index bc5d98f..e73427c 100644
--- a/test/test-mermaid.yaml
+++ b/test/test-mermaid.yaml
@@ -5,6 +5,10 @@ to: html
 metadata:
   pagetitle: Mermaid diagram
   diagram:
-    cache: false
+  engine:
+    mermaid:
+      execpath: /usr/local/bin/mmdc
+      puppeteerConfigFile: /etc/puppeteer-conf.json
 variables:
   document-css: false
+embed-resources: true