diff --git a/appveyor.yml b/appveyor.yml
index bc3ffa6c9..7b4d943de 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -4,7 +4,11 @@ clone_depth: 5
 build: off
 matrix:
   fast_finish: true
-
+  allow_failures:
+    - ruby_version: "25"
+    - ruby_version: "26"
+    - ruby_version: "27"
+    - ruby_version: "27-x64"
 services:
   - mssql2014
 
diff --git a/lib/active_record/connection_adapters/sqlserver/database_statements.rb b/lib/active_record/connection_adapters/sqlserver/database_statements.rb
index 68813c489..20e0df011 100644
--- a/lib/active_record/connection_adapters/sqlserver/database_statements.rb
+++ b/lib/active_record/connection_adapters/sqlserver/database_statements.rb
@@ -350,7 +350,12 @@ def sp_executesql_sql(sql, types, params, name)
         def raw_connection_do(sql)
           case @connection_options[:mode]
           when :dblib
-            @connection.execute(sql).do
+            result = @connection.execute(sql)
+            # If connection fails then TinyTDS returns false instead of an exception (see https://github.com/rails-sqlserver/tiny_tds/issues/464)
+            if result == false
+              raise TinyTds::Error, 'TinyTDS execute returned false instead of results'
+            end
+            result.do
           end
         ensure
           @update_sql = false