diff --git a/RELEASE.md b/RELEASE.md
new file mode 100644
index 0000000..6b3a9d2
--- /dev/null
+++ b/RELEASE.md
@@ -0,0 +1,3 @@
+Release type: patch
+
+Support `SITEURL` values that contain slugs after the domain
diff --git a/pelican/plugins/seo/seo_enhancer/html_enhancer/open_graph.py b/pelican/plugins/seo/seo_enhancer/html_enhancer/open_graph.py
index 23184c0..58b3ac0 100644
--- a/pelican/plugins/seo/seo_enhancer/html_enhancer/open_graph.py
+++ b/pelican/plugins/seo/seo_enhancer/html_enhancer/open_graph.py
@@ -21,6 +21,11 @@ def __init__(
 
     def _create_absolute_fileurl(self):
         """Join site URL and file path."""
+        if not self.siteurl.endswith("/"):
+            self.siteurl += "/"
+
+        if self.fileurl.startswith("/"):
+            self.fileurl = self.fileurl[1:]
 
         file_url = parse.urljoin(self.siteurl, self.fileurl)
         return file_url
diff --git a/pelican/plugins/seo/tests/test_open_graph.py b/pelican/plugins/seo/tests/test_open_graph.py
index b103cae..9e8d18a 100644
--- a/pelican/plugins/seo/tests/test_open_graph.py
+++ b/pelican/plugins/seo/tests/test_open_graph.py
@@ -29,6 +29,28 @@ def test_create_absolute_fileurl(self, fake_article):
 
         assert fileurl == "https://www.fakesite.com/fake-title.html"
 
+    @pytest.mark.parametrize(
+        "site_url", ["https://fake.github.io/blog", "https://fake.github.io/blog/"]
+    )
+    @pytest.mark.parametrize("file_url", ["fake-title.html", "/fake-title.html"])
+    def test_create_absolute_fileurl_with_site_url_with_path(self, site_url, file_url):
+        """
+        Test if create_absolute_fileurl() joins a site URL with or without a trailing
+        slash and a file URL with or without a leading slash properly.
+        """
+        og = OpenGraph(
+            siteurl=site_url,
+            fileurl=file_url,
+            file_type=None,
+            title=None,
+            description=None,
+            image=None,
+            locale=None,
+        )
+        fileurl = og._create_absolute_fileurl()
+
+        assert fileurl == "https://fake.github.io/blog/fake-title.html"
+
     @pytest.mark.parametrize(
         "locale,expected_result",
         [