diff --git a/.gitignore b/.gitignore
index 95f9ee9..5febb39 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@ lib-cov
 logs
 node_modules
 temp
+.history
diff --git a/src/syntax/block.ts b/src/syntax/block.ts
index 49d7abc..40f3de1 100644
--- a/src/syntax/block.ts
+++ b/src/syntax/block.ts
@@ -329,7 +329,7 @@ export const MarkdownItMdcBlock: MarkdownIt.PluginSimple = (md) => {
 
       const start = state.bMarks[startLine] + state.tShift[startLine]
 
-      if (!(state.src[start] === '#' && state.src[start + 1] !== ' '))
+      if (!(state.src[start] === '#' && state.src[start + 1] !== ' ' && state.src[start + 1] !== '#'))
         return false
 
       const line = state.src.slice(start, state.eMarks[startLine])
diff --git a/test/input/16.blocks-headings-in-slots.md b/test/input/16.blocks-headings-in-slots.md
new file mode 100644
index 0000000..7931e4f
--- /dev/null
+++ b/test/input/16.blocks-headings-in-slots.md
@@ -0,0 +1,9 @@
+::step
+### Step 1
+
+Content for step 1.
+
+### Step2
+
+More content.
+::
diff --git a/test/output/1.basic.html b/test/output/1.basic.html
index 3ff1823..db6ad36 100644
--- a/test/output/1.basic.html
+++ b/test/output/1.basic.html
@@ -14,8 +14,8 @@ <h1>Hello</h1>
 </blockquote>
 <pre><code class="language-bash">npm i @comark/markdown-it
 </code></pre>
-<pre><code class="language-ts">import MarkdownIt from 'markdown-it'
-import mdc from '@comark/markdown-it'
+<pre><code class="language-ts">import mdc from '@comark/markdown-it'
+import MarkdownIt from 'markdown-it'
 
 // :warning: this line should not be transformed
 const md = new MarkdownIt()
diff --git a/test/output/16.blocks-headings-in-slots.html b/test/output/16.blocks-headings-in-slots.html
new file mode 100644
index 0000000..bb7838b
--- /dev/null
+++ b/test/output/16.blocks-headings-in-slots.html
@@ -0,0 +1,6 @@
+<step>
+  <h3>Step 1</h3>
+  <p>Content for step 1.</p>
+  <h3>Step2</h3>
+  <p>More content.</p>
+</step>
\ No newline at end of file