diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index be48c6b86..bf57c7302 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -13,6 +13,10 @@ For a detailed view of what has changed, refer to the {url-repo}/commits/main[co
 
 == Unreleased
 
+Improvement::
+
+* Upgrade to asciidoctorj 2.0.18 (#1126)
+
 == 2.5.6 (2022-09-19)
 
 Improvement::
diff --git a/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionGroupIsRegistered.java b/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionGroupIsRegistered.java
index cadb68061..87898d0d4 100644
--- a/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionGroupIsRegistered.java
+++ b/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionGroupIsRegistered.java
@@ -46,10 +46,11 @@
 import static org.hamcrest.CoreMatchers.not;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.hamcrest.CoreMatchers.startsWith;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.hasSize;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 
 @RunWith(Arquillian.class)
@@ -111,8 +112,6 @@ private StringBuilder readContent(String target) {
 
                 bufferedReader.close();
 
-            } catch (MalformedURLException e) {
-                throw new IllegalArgumentException(e);
             } catch (IOException e) {
                 throw new IllegalArgumentException(e);
             }
@@ -180,8 +179,6 @@ private StringBuilder readContent(String target) {
 
                     bufferedReader.close();
 
-                } catch (MalformedURLException e) {
-                    throw new IllegalArgumentException(e);
                 } catch (IOException e) {
                     throw new IllegalArgumentException(e);
                 }
@@ -242,7 +239,7 @@ public void a_docinfoprocessor_should_be_executed_and_add_meta_in_footer() {
 
         Element footer = doc.getElementById("footer");
         // Since Asciidoctor 1.5.3 the docinfo in the footer is a sibling to the footer element
-        assertTrue("robots".equals(footer.nextElementSibling().attr("name")));
+        assertEquals("robots", footer.nextElementSibling().attr("name"));
     }
 
     @Test
@@ -436,7 +433,7 @@ public void a_include_processor_should_only_handle_its_handles() {
 
         org.jsoup.nodes.Document doc = Jsoup.parse(content, "UTF-8");
 
-        Element contentElement = doc.getElementsByAttributeValue("class", "bare").first();
+        Element contentElement = doc.getElementsByClass("bare").first();
 
         assertThat(contentElement.text(), startsWith("sample-book.adoc"));
 
diff --git a/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionIsRegistered.java b/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionIsRegistered.java
index b121dc191..7cd18bd13 100644
--- a/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionIsRegistered.java
+++ b/asciidoctorj-core/src/test/java/org/asciidoctor/extension/WhenJavaExtensionIsRegistered.java
@@ -47,12 +47,12 @@
 import static org.hamcrest.CoreMatchers.not;
 import static org.hamcrest.CoreMatchers.notNullValue;
 import static org.hamcrest.CoreMatchers.startsWith;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.hasSize;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
 
 @RunWith(Arquillian.class)
 public class WhenJavaExtensionIsRegistered {
@@ -239,7 +239,7 @@ public void a_docinfoprocessor_should_be_executed_and_add_meta_in_footer() {
 
         Element footer = doc.getElementById("footer");
         // Since Asciidoctor 1.5.3 the docinfo in the footer is a sibling to the footer element
-        assertTrue("robots".equals(footer.nextElementSibling().attr("name")));
+        assertEquals("robots", footer.nextElementSibling().attr("name"));
     }
 
     @Test
@@ -429,11 +429,11 @@ public void a_include_processor_should_only_handle_its_handles() {
         javaExtensionRegistry.includeProcessor(UriIncludeProcessor.class);
 
         String content = asciidoctor.convertFile(classpath.getResource("sample-with-include.ad"),
-                options().toFile(false).get());
+                Options.builder().toFile(false).build());
 
         org.jsoup.nodes.Document doc = Jsoup.parse(content, "UTF-8");
 
-        Element contentElement = doc.getElementsByAttributeValue("class", "bare").first();
+        Element contentElement = doc.getElementsByClass("bare").first();
 
         assertThat(contentElement.text(), startsWith("sample-book.adoc"));
 
diff --git a/build.gradle b/build.gradle
index 61e9ed782..f9455eaa7 100644
--- a/build.gradle
+++ b/build.gradle
@@ -79,8 +79,8 @@ ext {
   pdfboxVersion = '1.8.16'
 
   // gem versions
-  asciidoctorGemVersion = project.hasProperty('asciidoctorGemVersion') ? project.asciidoctorGemVersion : '2.0.17'
-  asciimathGemVersion = '2.0.3'
+  asciidoctorGemVersion = project.hasProperty('asciidoctorGemVersion') ? project.asciidoctorGemVersion : '2.0.18'
+  asciimathGemVersion = '2.0.4'
   coderayGemVersion = '1.1.3'
   rougeGemVersion = '3.30.0'