diff --git a/middleman-core/lib/middleman-core/renderers/sass.rb b/middleman-core/lib/middleman-core/renderers/sass.rb
index <HASH>..<HASH> 100644
--- a/middleman-core/lib/middleman-core/renderers/sass.rb
+++ b/middleman-core/lib/middleman-core/renderers/sass.rb
@@ -61,6 +61,8 @@ module Middleman
             @engine.render
           rescue ::SassC::SyntaxError => e
             exception_to_css(e)
+
+            raise e if @context.app.build?
           end
         end
 
@@ -93,8 +95,14 @@ module Middleman
         def sass_options
           ctx = @context
 
+          preexisting_load_paths = begin
+            ::Sass.load_paths
+          rescue
+            []
+          end
+
           more_opts = {
-            load_paths: ctx.app.config[:sass_assets_paths],
+            load_paths: preexisting_load_paths + ctx.app.config[:sass_assets_paths],
             filename: eval_file,
             line: line,
             syntax: syntax,
Import paths from libraries which expect ::Sass module to still exist. Fixes #<I>