diff --git a/lib/gollum/tex.rb b/lib/gollum/tex.rb
index 71646fa9..7b0b60c4 100644
--- a/lib/gollum/tex.rb
+++ b/lib/gollum/tex.rb
@@ -54,16 +54,16 @@ module Gollum
         ::File.open(tex_path, 'w') { |f| f.write(Template % formula) }
 
         result = sh latex_path, '-interaction=batchmode', 'formula.tex', :cwd => path
-        raise "`latex` command failed: #{result}" unless ::File.exist?(eps_path)
+        raise Error, "`latex` command failed: #{result}" unless ::File.exist?(eps_path)
 
         result = sh dvips_path, '-o', eps_path, '-E', dvi_path
-        raise "`dvips` command failed: #{result}" unless ::File.exist?(dvi_path)
+        raise Error, "`dvips` command failed: #{result}" unless ::File.exist?(dvi_path)
         result = sh convert_path, '+adjoin',
           '-antialias',
           '-transparent', 'white',
           '-density', '150x150',
           eps_path, png_path
-        raise "`convert` command failed: #{result}" unless ::File.exist?(png_path)
+        raise Error, "`convert` command failed: #{result}" unless ::File.exist?(png_path)
 
         ::File.read(png_path)
       end