diff --git a/Gemfile.lock b/Gemfile.lock
index 7639e61..2f6d4af 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -9,42 +9,42 @@ PATH
 GEM
   remote: http://rubygems.org/
   specs:
-    Ascii85 (1.0.2)
+    Ascii85 (1.1.0)
     afm (0.2.2)
-    coderay (1.1.2)
-    diff-lcs (1.3)
+    coderay (1.1.3)
+    diff-lcs (1.5.0)
     hashery (2.1.2)
-    method_source (0.9.0)
+    method_source (1.0.0)
     pdf-inspector (1.3.0)
       pdf-reader (>= 1.0, < 3.0.a)
-    pdf-reader (2.0.0)
-      Ascii85 (~> 1.0.0)
+    pdf-reader (2.10.0)
+      Ascii85 (~> 1.0)
       afm (~> 0.2.1)
       hashery (~> 2.0)
       ruby-rc4
       ttfunk
-    pdfkit (0.8.2)
-    pry (0.11.3)
-      coderay (~> 1.1.0)
-      method_source (~> 0.9.0)
-    rake (12.3.3)
-    rouge (3.3.0)
-    rspec (3.7.0)
-      rspec-core (~> 3.7.0)
-      rspec-expectations (~> 3.7.0)
-      rspec-mocks (~> 3.7.0)
-    rspec-core (3.7.1)
-      rspec-support (~> 3.7.0)
-    rspec-expectations (3.7.0)
+    pdfkit (0.8.6)
+    pry (0.14.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    rake (13.0.6)
+    rouge (3.29.0)
+    rspec (3.11.0)
+      rspec-core (~> 3.11.0)
+      rspec-expectations (~> 3.11.0)
+      rspec-mocks (~> 3.11.0)
+    rspec-core (3.11.0)
+      rspec-support (~> 3.11.0)
+    rspec-expectations (3.11.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.7.0)
-    rspec-mocks (3.7.0)
+      rspec-support (~> 3.11.0)
+    rspec-mocks (3.11.1)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.7.0)
-    rspec-support (3.7.0)
+      rspec-support (~> 3.11.0)
+    rspec-support (3.11.0)
     ruby-rc4 (0.1.5)
-    ttfunk (1.5.1)
-    wkhtmltopdf-binary (0.12.4)
+    ttfunk (1.7.0)
+    wkhtmltopdf-binary (0.12.6.5)
 
 PLATFORMS
   ruby
@@ -58,4 +58,4 @@ DEPENDENCIES
   rspec
 
 BUNDLED WITH
-   1.17.1
+   2.3.16
diff --git a/lib/code2pdf/convert_to_pdf.rb b/lib/code2pdf/convert_to_pdf.rb
index 6885bcc..e8d9697 100644
--- a/lib/code2pdf/convert_to_pdf.rb
+++ b/lib/code2pdf/convert_to_pdf.rb
@@ -46,8 +46,8 @@ def pdf
   end
 
   def syntax_highlight(file)
-    file_type = File.extname(file.first)[1..-1]
-    file_lexer = Rouge::Lexer.find(file_type)
+    file_name = File.basename(file.first)
+    file_lexer = Rouge::Lexer.guess_by_filename(file_name)
     return CGI.escapeHTML(file.last) unless file_lexer
 
     theme = Rouge::Themes::Base16.mode(:light)
diff --git a/spec/fixtures/hello_world/lib/sample.kt b/spec/fixtures/hello_world/lib/sample.kt
new file mode 100644
index 0000000..b0a1cbd
--- /dev/null
+++ b/spec/fixtures/hello_world/lib/sample.kt
@@ -0,0 +1,8 @@
+/**
+ * Some javadoc
+ */
+class Example {
+    fun sum(): Int {
+        return 2 + 2
+    }
+}
diff --git a/spec/fixtures/hello_world_original.pdf b/spec/fixtures/hello_world_original.pdf
index 867e913..b8e3db5 100644
Binary files a/spec/fixtures/hello_world_original.pdf and b/spec/fixtures/hello_world_original.pdf differ