diff --git a/app/models/query.rb b/app/models/query.rb
index 1f033048..1772d68f 100644
--- a/app/models/query.rb
+++ b/app/models/query.rb
@@ -566,9 +566,19 @@ class Query < ActiveRecord::Base
     sql = ''
     case operator
     when "="
-      sql = "#{db_table}.#{db_field} IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + ")"
+      if value.present?
+        sql = "#{db_table}.#{db_field} IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + ")"
+      else
+        # empty set of allowed values produces no result
+        sql = "0=1"
+      end
     when "!"
-      sql = "(#{db_table}.#{db_field} IS NULL OR #{db_table}.#{db_field} NOT IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + "))"
+      if value.present?
+        sql = "(#{db_table}.#{db_field} IS NULL OR #{db_table}.#{db_field} NOT IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + "))"
+      else
+        # empty set of forbidden values allows all results
+        sql = "1=1"
+      end
     when "!*"
       sql = "#{db_table}.#{db_field} IS NULL"
       sql << " OR #{db_table}.#{db_field} = ''" if is_custom_filter
diff --git a/test/unit/query_test.rb b/test/unit/query_test.rb
index 4d85a2b2..a20c14e9 100644
--- a/test/unit/query_test.rb
+++ b/test/unit/query_test.rb
@@ -467,6 +467,7 @@ class QueryTest < ActiveSupport::TestCase
         @group2 = Group.generate!.reload
         @group2.users << @user_in_group2
         
+        @empty_group = Group.generate!.reload
       end
       
       should "search assigned to for users in the group" do
@@ -484,7 +485,6 @@ class QueryTest < ActiveSupport::TestCase
         # Users not in a group
         assert_query_statement_includes @query, "#{Issue.table_name}.assigned_to_id IS NULL OR #{Issue.table_name}.assigned_to_id NOT IN ('#{@user_in_group.id}','#{@second_user_in_group.id}','#{@user_in_group2.id}')"
         assert_find_issues_with_query_is_successful @query
-
       end
 
       should "search assigned to any group member (all)" do
@@ -494,7 +494,22 @@ class QueryTest < ActiveSupport::TestCase
         # Only users in a group
         assert_query_statement_includes @query, "#{Issue.table_name}.assigned_to_id IN ('#{@user_in_group.id}','#{@second_user_in_group.id}','#{@user_in_group2.id}')"
         assert_find_issues_with_query_is_successful @query
-
+      end
+      
+      should "return no results on empty set" do
+        @query = Query.new(:name => '_')
+        @query.add_filter('member_of_group', '=', [@empty_group.id.to_s])
+        
+        assert_query_statement_includes @query, "(0=1)"
+        assert find_issues_with_query(@query).empty?
+      end
+      
+      should "return results on disallowed empty set" do
+        @query = Query.new(:name => '_')
+        @query.add_filter('member_of_group', '!', [@empty_group.id.to_s])
+        
+        assert_query_statement_includes @query, "(1=1)"
+        assert_find_issues_with_query_is_successful @query
       end
     end
 
@@ -507,6 +522,7 @@ class QueryTest < ActiveSupport::TestCase
         
         @manager_role = Role.generate!(:name => 'Manager')
         @developer_role = Role.generate!(:name => 'Developer')
+        @empty_role = Role.generate!(:name => 'Empty')
 
         @project = Project.generate!
         @manager = User.generate!
@@ -540,6 +556,22 @@ class QueryTest < ActiveSupport::TestCase
         assert_query_statement_includes @query, "#{Issue.table_name}.assigned_to_id IN ('#{@manager.id}','#{@developer.id}','#{@boss.id}')"
         assert_find_issues_with_query_is_successful @query
       end
+
+      should "return no results on empty set" do
+        @query = Query.new(:name => '_')
+        @query.add_filter('assigned_to_role', '=', [@empty_role.id.to_s])
+        
+        assert_query_statement_includes @query, "(0=1)"
+        assert find_issues_with_query(@query).empty?
+      end
+      
+      should "return results on disallowed empty set" do
+        @query = Query.new(:name => '_')
+        @query.add_filter('assigned_to_role', '!', [@empty_role.id.to_s])
+        
+        assert_query_statement_includes @query, "(1=1)"
+        assert_find_issues_with_query_is_successful @query
+      end
     end
   end