diff --git a/app/models/profile_list_block.rb b/app/models/profile_list_block.rb
index 450d33b..92ebf07 100644
--- a/app/models/profile_list_block.rb
+++ b/app/models/profile_list_block.rb
@@ -21,7 +21,7 @@ class ProfileListBlock < Block
   end
 
   def randomizer
-    @randomizer ||= "(profiles.id % #{rand(profile_count + 1)})"
+    @randomizer ||= "(profiles.id % #{rand(profile_count) + 1})"
   end
 
   # the title of the block. Probably will be overriden in subclasses.
diff --git a/test/unit/profile_list_block_test.rb b/test/unit/profile_list_block_test.rb
index 9d50df8..a052085 100644
--- a/test/unit/profile_list_block_test.rb
+++ b/test/unit/profile_list_block_test.rb
@@ -153,8 +153,15 @@ class ProfileListBlockTest < Test::Unit::TestCase
   should 'randomize using modulo operator and random number' do
     block = ProfileListBlock.new
     block.expects(:profile_count).returns(10)
-    block.expects(:rand).with(11).returns(5)
-    assert_match /profiles.id % 5/, block.randomizer
+    block.expects(:rand).with(10).returns(5)
+    assert_match /profiles.id % 6/, block.randomizer
+  end
+
+  should 'not divide by zero' do
+    block = ProfileListBlock.new
+    block.stubs(:profile_count).returns(0)
+    block.expects(:rand).returns(0)
+    assert_no_match /profiles.id % 0/, block.randomizer
   end
 
 end
--
libgit2 0.21.2