diff --git a/asciidoctorj-pdf/gradle.properties b/asciidoctorj-pdf/gradle.properties
index e52be96..fe3a8b6 100644
--- a/asciidoctorj-pdf/gradle.properties
+++ b/asciidoctorj-pdf/gradle.properties
@@ -1,4 +1,4 @@
 properName=AsciidoctorJ PDF
 description=AsciidoctorJ PDF bundles the Asciidoctor PDF RubyGem (asciidoctor-pdf) so it can be loaded into the JVM using JRuby.
-version=2.3.7
+version=2.3.9
 gem_name=asciidoctor-pdf
diff --git a/build.gradle b/build.gradle
index 89823f9..ee56857 100644
--- a/build.gradle
+++ b/build.gradle
@@ -40,7 +40,7 @@ ext {
 
   // gem versions
   asciidoctorJVersion = project.hasProperty('asciidoctorJVersion') ? project.asciidoctorJVersion : '2.5.7'
-  asciidoctorPdfGemVersion = project.hasProperty('asciidoctorPdfGemVersion') ? project.asciidoctorPdfGemVersion : '2.3.7'
+  asciidoctorPdfGemVersion = project.hasProperty('asciidoctorPdfGemVersion') ? project.asciidoctorPdfGemVersion : '2.3.9'
 
   addressableVersion = '2.8.0'
   concurrentRubyVersion = '1.1.7'
diff --git a/gradle.properties b/gradle.properties
index 53ca44a..d6dac92 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,3 +1,3 @@
-version=2.3.7
+version=2.3.9
 sourceCompatibility=1.8
 targetCompatibility=1.8