diff --git a/.travis.yml b/.travis.yml
index d8a0a35..25ae39d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -16,6 +16,7 @@ script:
   - yarn build
   # tests
   - yarn test
+  - yarn readme:check
 
 deploy:
   - provider: script
diff --git a/README.md b/README.md
index 035e278..c12bdc8 100644
--- a/README.md
+++ b/README.md
@@ -30,15 +30,16 @@ npx embedme README.md
 
 Et voilà! Your README.md file will be updated with the content of your source file:
 
+<!-- prettier-ignore -->
     This is a *markdown* document with a code block:
 
     ```ts
     // example.ts
-
+    
     export function helloWorld(name: string): string {
       return `Hello ${name}!, how are you today?`;
     }
-
+    
     ```
 
 As the comment is preserved, you can happily re-run `embedme` and it will run again but there will be no changes.
@@ -78,14 +79,14 @@ Here's a list of file types supported by this utility, if you have a need for an
 contribute, it is easy!
 
 ```ts
-// src/embedme.lib.ts#L44-L71
+// src/embedme.lib.ts#L44-L73
 
 enum SupportedFileType {
   PLAIN_TEXT = 'txt',
   TYPESCRIPT = 'ts',
   JAVASCRIPT = 'js',
   SCSS = 'scss',
-  RUST = 'rs',
+  RUST = 'rust',
   JAVA = 'java',
   CPP = 'cpp',
   C = 'c',
@@ -107,6 +108,8 @@ enum SupportedFileType {
   KOTLIN = 'kotlin',
   SCALA = 'scala',
   CRYSTAL = 'cr',
+  PLANT_UML = 'puml',
+  MERMAID = 'mermaid',
 }
 ```
 
diff --git a/src/embedme.lib.ts b/src/embedme.lib.ts
index 3ac278b..32b1ef9 100644
--- a/src/embedme.lib.ts
+++ b/src/embedme.lib.ts
@@ -69,6 +69,7 @@ enum SupportedFileType {
   SCALA = 'scala',
   CRYSTAL = 'cr',
   PLANT_UML = 'puml',
+  MERMAID = 'mermaid',
 }
 
 enum CommentFamily {
@@ -77,6 +78,7 @@ enum CommentFamily {
   XML,
   HASH,
   SINGLE_QUOTE,
+  DOUBLE_PERCENT,
 }
 
 const languageMap: Record<CommentFamily, SupportedFileType[]> = {
@@ -109,18 +111,23 @@ const languageMap: Record<CommentFamily, SupportedFileType[]> = {
     SupportedFileType.CRYSTAL,
   ],
   [CommentFamily.SINGLE_QUOTE]: [SupportedFileType.PLANT_UML],
+  [CommentFamily.DOUBLE_PERCENT]: [SupportedFileType.MERMAID],
+};
+
+const leadingSymbol = (symbol: string): FilenameFromCommentReader => line => {
+  const regex = new RegExp(`${symbol}\\s?(\\S*?$)`);
+
+  const match = line.match(regex);
+  if (!match) {
+    return null;
+  }
+
+  return match[1];
 };
 
 const filetypeCommentReaders: Record<CommentFamily, FilenameFromCommentReader> = {
   [CommentFamily.NONE]: _ => null,
-  [CommentFamily.C]: line => {
-    const match = line.match(/\/\/\s?(\S*?$)/m);
-    if (!match) {
-      return null;
-    }
-
-    return match[1];
-  },
+  [CommentFamily.C]: leadingSymbol('//'),
   [CommentFamily.XML]: line => {
     const match = line.match(/<!--\s*?(\S*?)\s*?-->/);
     if (!match) {
@@ -129,22 +136,9 @@ const filetypeCommentReaders: Record<CommentFamily, FilenameFromCommentReader> =
 
     return match[1];
   },
-  [CommentFamily.HASH]: line => {
-    const match = line.match(/#\s*?(\S*?)$/);
-    if (!match) {
-      return null;
-    }
-
-    return match[1];
-  },
-  [CommentFamily.SINGLE_QUOTE]: line => {
-    const match = line.match(/'\s*?(\S*?)$/);
-    if (!match) {
-      return null;
-    }
-
-    return match[1];
-  },
+  [CommentFamily.HASH]: leadingSymbol('#'),
+  [CommentFamily.SINGLE_QUOTE]: leadingSymbol('//'),
+  [CommentFamily.DOUBLE_PERCENT]: leadingSymbol('%%'),
 };
 
 function lookupLanguageCommentFamily(fileType: SupportedFileType): CommentFamily | null {
diff --git a/test/fixture.md b/test/fixture.md
index d6444b6..64e7fc9 100644
--- a/test/fixture.md
+++ b/test/fixture.md
@@ -304,6 +304,23 @@ return bye
 
 ```
 
+Mermaid
+
+```mermaid
+%% sample.mermaid
+
+sequenceDiagram
+    Alice ->> Bob: Hello Bob, how are you?
+    Bob-->>John: How about you John?
+    Bob--x Alice: I am good thanks!
+    Bob-x John: I am good thanks!
+    Note right of John: Bob thinks a long<br/>long time, so long<br/>that the text does<br/>not fit on a row.
+
+    Bob-->Alice: Checking with John...
+    Alice->John: Yes... John, how are you?
+
+```
+
 ## Extension-less selection
 
 ```sh
diff --git a/test/sample.mermaid b/test/sample.mermaid
new file mode 100644
index 0000000..52402cc
--- /dev/null
+++ b/test/sample.mermaid
@@ -0,0 +1,9 @@
+sequenceDiagram
+    Alice ->> Bob: Hello Bob, how are you?
+    Bob-->>John: How about you John?
+    Bob--x Alice: I am good thanks!
+    Bob-x John: I am good thanks!
+    Note right of John: Bob thinks a long<br/>long time, so long<br/>that the text does<br/>not fit on a row.
+
+    Bob-->Alice: Checking with John...
+    Alice->John: Yes... John, how are you?