diff --git a/middleman-core/fixtures/asset-host-app/source/javascripts/asset_host.js b/middleman-core/fixtures/asset-host-app/source/javascripts/asset_host.js
new file mode 100644
index 00000000..251ce693
--- /dev/null
+++ b/middleman-core/fixtures/asset-host-app/source/javascripts/asset_host.js
@@ -0,0 +1,2 @@
+var a = jQuery.css("h1", "font-size");
+console.log(a);
diff --git a/middleman-core/lib/middleman-core/sources/source_watcher.rb b/middleman-core/lib/middleman-core/sources/source_watcher.rb
index e1a3fdd4..cb163abd 100644
--- a/middleman-core/lib/middleman-core/sources/source_watcher.rb
+++ b/middleman-core/lib/middleman-core/sources/source_watcher.rb
@@ -49,6 +49,8 @@ module Middleman
     # Reference to lower level listener
     attr_reader :listener
 
+    IGNORED_DIRECTORIES = %w(.git node_modules .sass-cache)
+
     # Construct a new SourceWatcher
     #
     # @param [Middleman::Sources] parent The parent collection.
@@ -182,7 +184,7 @@ module Middleman
 
     Contract ArrayOf[Pathname]
     def find_new_files!
-      new_files = ::Middleman::Util.all_files_under(@directory.to_s)
+      new_files = ::Middleman::Util.all_files_under(@directory.to_s, &method(:should_not_recurse?))
                                    .reject { |p| @files.key?(p) }
 
       update(new_files, []).flatten.map { |s| s[:full_path] }
@@ -193,7 +195,7 @@ module Middleman
     # @return [void]
     Contract ArrayOf[Pathname]
     def poll_once!
-      updated = ::Middleman::Util.all_files_under(@directory.to_s)
+      updated = ::Middleman::Util.all_files_under(@directory.to_s, &method(:should_not_recurse?))
       removed = @files.keys.reject { |p| updated.include?(p) }
 
       result = update(updated, removed)
@@ -217,6 +219,11 @@ module Middleman
 
     protected
 
+    Contract Pathname => Bool
+    def should_not_recurse?(p)
+      IGNORED_DIRECTORIES.include?(p.basename.to_s)
+    end
+
     # The `listen` gem callback.
     #
     # @param [Array] modified List of modified files.
diff --git a/middleman-core/lib/middleman-core/util.rb b/middleman-core/lib/middleman-core/util.rb
index cfbcb9ee..f0ca99cd 100644
--- a/middleman-core/lib/middleman-core/util.rb
+++ b/middleman-core/lib/middleman-core/util.rb
@@ -156,16 +156,14 @@ module Middleman
     def all_files_under(path, &ignore)
       path = Pathname(path)
 
-      if path.directory?
+      if ignore && ignore.call(path)
+        []
+      elsif path.directory?
         path.children.flat_map do |child|
           all_files_under(child, &ignore)
         end.compact
       elsif path.file?
-        if block_given? && yield(path)
-          []
-        else
-          [path]
-        end
+        [path]
       else
         []
       end