diff --git a/README.md b/README.md
index 802f0f0..07542b0 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,7 @@ FillablePDF is an extremely simple and lightweight utility that bridges iText an
 
 **Prerequisites:** Java SE Development Kit v8, v11
 
-- Ensure that your `JAVA_HOME` variable is set before installing this gem (see examples below).**
+- Ensure that your `JAVA_HOME` variable is set before installing this gem (see examples below).
 
   * OSX: `/Library/Java/JavaVirtualMachines/jdk-11.0.2.jdk/Contents/Home`
   * Ubuntu/CentOS: `/usr/lib/jvm/java-1.8.0-openjdk`
diff --git a/example/output.flat.pdf b/example/output.flat.pdf
index f61f675..d86656f 100644
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diff --git a/example/output.pdf b/example/output.pdf
index 2f591a0..98c2fc3 100644
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diff --git a/ext/commons-7.2.3.jar b/ext/commons-7.2.3.jar
new file mode 100755
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diff --git a/ext/font-asian-7.1.17.jar b/ext/font-asian-7.2.3.jar
similarity index 98%
rename from ext/font-asian-7.1.17.jar
rename to ext/font-asian-7.2.3.jar
index 73fb081..17053cd 100755
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diff --git a/ext/forms-7.1.17.jar b/ext/forms-7.1.17.jar
deleted file mode 100755
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diff --git a/ext/forms-7.2.3.jar b/ext/forms-7.2.3.jar
new file mode 100755
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diff --git a/ext/io-7.1.17.jar b/ext/io-7.1.17.jar
deleted file mode 100755
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diff --git a/ext/io-7.2.3.jar b/ext/io-7.2.3.jar
new file mode 100755
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diff --git a/ext/kernel-7.1.17.jar b/ext/kernel-7.1.17.jar
deleted file mode 100755
index b6826fd..0000000
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diff --git a/ext/kernel-7.2.3.jar b/ext/kernel-7.2.3.jar
new file mode 100755
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diff --git a/ext/layout-7.1.17.jar b/ext/layout-7.1.17.jar
deleted file mode 100755
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diff --git a/ext/layout-7.2.3.jar b/ext/layout-7.2.3.jar
new file mode 100755
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diff --git a/fillable-pdf.gemspec b/fillable-pdf.gemspec
index dae58b6..d59f405 100644
--- a/fillable-pdf.gemspec
+++ b/fillable-pdf.gemspec
@@ -30,7 +30,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rubocop-performance'
   spec.add_development_dependency 'rubocop-rake'
 
-  spec.add_runtime_dependency 'rjb', '1.6.2'
+  spec.add_runtime_dependency 'rjb', '~> 1.6'
+  spec.requirements << 'JDK 8.x - 11.x'
 
   spec.metadata = {
     'rubygems_mfa_required' => 'true'
diff --git a/lib/fillable-pdf.rb b/lib/fillable-pdf.rb
index fc580a6..8134c6b 100644
--- a/lib/fillable-pdf.rb
+++ b/lib/fillable-pdf.rb
@@ -145,7 +145,7 @@ def set_image(key, file_path) # rubocop:disable Metrics/AbcSize, Metrics/MethodL
   #
   def set_image_base64(key, base64_image_data)
     tmp_file = SecureRandom.uuid
-    File.open(tmp_file, 'wb') { |f| f.write(Base64.decode64(base64_image_data)) }
+    File.binwrite(tmp_file, Base64.decode64(base64_image_data))
     set_image(key, tmp_file)
   ensure
     FileUtils.rm tmp_file
diff --git a/lib/fillable-pdf/itext.rb b/lib/fillable-pdf/itext.rb
index 10c2eed..2f3150b 100644
--- a/lib/fillable-pdf/itext.rb
+++ b/lib/fillable-pdf/itext.rb
@@ -8,7 +8,7 @@ module ITEXT
     ByteArrayOutputStream = Rjb.import 'com.itextpdf.io.source.ByteArrayOutputStream'
     Canvas = Rjb.import 'com.itextpdf.layout.Canvas'
     Div = Rjb.import 'com.itextpdf.layout.element.Div'
-    HorizontalAlignment = Rjb.import 'com.itextpdf.layout.property.HorizontalAlignment'
+    HorizontalAlignment = Rjb.import 'com.itextpdf.layout.properties.HorizontalAlignment'
     Image = Rjb.import 'com.itextpdf.layout.element.Image'
     ImageDataFactory = Rjb.import 'com.itextpdf.io.image.ImageDataFactory'
     PdfAcroForm = Rjb.import 'com.itextpdf.forms.PdfAcroForm'
@@ -19,6 +19,6 @@ module ITEXT
     PdfReader = Rjb.import 'com.itextpdf.kernel.pdf.PdfReader'
     PdfWriter = Rjb.import 'com.itextpdf.kernel.pdf.PdfWriter'
     Rectangle = Rjb.import 'com.itextpdf.kernel.geom.Rectangle'
-    VerticalAlignment = Rjb.import 'com.itextpdf.layout.property.VerticalAlignment'
+    VerticalAlignment = Rjb.import 'com.itextpdf.layout.properties.VerticalAlignment'
   end
 end
diff --git a/lib/fillable-pdf/version.rb b/lib/fillable-pdf/version.rb
index 78c23cc..d64c2f2 100644
--- a/lib/fillable-pdf/version.rb
+++ b/lib/fillable-pdf/version.rb
@@ -1,3 +1,3 @@
 class FillablePDF
-  VERSION = '0.9.3'
+  VERSION = '0.9.4'
 end
diff --git a/test/pdf_test.rb b/test/pdf_test.rb
index 365f9f6..8fb0f72 100644
--- a/test/pdf_test.rb
+++ b/test/pdf_test.rb
@@ -23,11 +23,11 @@ def test_that_an_error_is_thrown_for_non_existing_file
   end
 
   def test_that_file_has_editable_fields
-    assert @pdf.any_fields?
+    assert_predicate @pdf, :any_fields?
   end
 
   def test_that_file_has_a_positive_number_of_editable_fields
-    assert @pdf.num_fields.positive?
+    assert_predicate @pdf.num_fields, :positive?
   end
 
   def test_that_hash_can_be_accessed