diff --git a/Gemfile.lock b/Gemfile.lock
index 41740b2f..7b1f8fbc 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -7,9 +7,12 @@ PATH
       genevalidatorapp (~> 2.1.8)
       matrix (~> 0.4.2)
       net-ftp (~> 0.1.3)
+      prime (~> 0.1.2)
       rack (~> 2.0)
+      rexml (~> 3.2, >= 3.2.6)
       slim (~> 3.0)
       statsample (= 2.1.0)
+      webrick (~> 1.8)
 
 GEM
   remote: http://rubygems.org/
@@ -31,6 +34,7 @@ GEM
     distribution (0.8.0)
     docile (1.4.0)
     extendmatrix (0.4)
+    forwardable (1.3.3)
     genevalidatorapp (2.1.8)
       bio (~> 1.4)
       sinatra (~> 2.0)
@@ -61,6 +65,9 @@ GEM
     prawn-security (0.8.4)
     prawn-svg (0.9.1.11)
       prawn (>= 0.8.4)
+    prime (0.1.2)
+      forwardable
+      singleton
     racc (1.7.3)
     rack (2.2.8)
     rack-protection (2.2.4)
@@ -71,6 +78,7 @@ GEM
       prawn (~> 0.8.4)
       prawn-svg (~> 0.9.1)
       text-table (~> 1.2)
+    rexml (3.2.6)
     rserve-client (0.3.5)
     ruby-ole (1.2.12.2)
     ruby2_keywords (0.0.5)
@@ -87,6 +95,7 @@ GEM
       rack-protection (= 2.2.4)
       tilt (~> 2.0)
     sinatra-cross_origin (0.4.0)
+    singleton (0.1.1)
     slim (3.0.9)
       temple (>= 0.7.6, < 0.9)
       tilt (>= 1.3.3, < 2.1)
@@ -110,6 +119,7 @@ GEM
     time (0.3.0)
       date
     timeout (0.4.1)
+    webrick (1.8.1)
     yard (0.9.34)
 
 PLATFORMS
diff --git a/genevalidator.gemspec b/genevalidator.gemspec
index 35f43486..1b616a42 100644
--- a/genevalidator.gemspec
+++ b/genevalidator.gemspec
@@ -26,9 +26,12 @@ Gem::Specification.new do |s|
   s.add_dependency 'genevalidatorapp', '~> 2.1.8'
   s.add_dependency 'matrix', '~> 0.4.2' # required by statsample
   s.add_dependency 'net-ftp', '~> 0.1.3' # required by ncbi-blast-dbs
+  s.add_dependency 'prime', '~> 0.1.2' # required by distribution (statsample)
   s.add_dependency 'rack', '~> 2.0'
   s.add_dependency 'slim', '~>3.0'
   s.add_dependency 'statsample', '2.1.0'
+  s.add_dependency 'rexml', '~> 3.2', '>= 3.2.6' # required by prawn (statsample)
+  s.add_dependency 'webrick', '~> 1.8'
 
   s.files         = `git ls-files -z`.split("\x0")
   s.executables   = s.files.grep(%r{^bin/}) { |f| File.basename(f) }
diff --git a/lib/genevalidator/ext/file.rb b/lib/genevalidator/ext/file.rb
new file mode 100644
index 00000000..e0d87c0f
--- /dev/null
+++ b/lib/genevalidator/ext/file.rb
@@ -0,0 +1,6 @@
+# Needed for Prawn (from Statsample)
+class File
+  class << self
+    alias_method :exists?, :exist? unless respond_to?(:exists?)
+  end
+end
diff --git a/lib/genevalidator/validation.rb b/lib/genevalidator/validation.rb
index 12fec5eb..1f79a344 100644
--- a/lib/genevalidator/validation.rb
+++ b/lib/genevalidator/validation.rb
@@ -1,5 +1,7 @@
 require 'forwardable'
-# Statsample: must loaded before /ext/array as they modify a built-in class
+# Statsample: must loaded after ext/file as they use a deprecated method - File.exists?
+# And before /ext/array as they modify a built-in class
+require 'genevalidator/ext/file'
 require 'statsample'
 
 require 'genevalidator/blast'