diff --git a/lib/carto/renderer.js b/lib/carto/renderer.js
index 2297c19..ce14af1 100644
--- a/lib/carto/renderer.js
+++ b/lib/carto/renderer.js
@@ -228,7 +228,8 @@ carto.Renderer.prototype.render = function render(m, callback) {
 //
 // @param {Array} the current list of rules
 // @param {Object} definition a Definition object to add to the rules
-// @param {Object} byFilter an object/dictionary of existing filters
+// @param {Object} byFilter an object/dictionary of existing filters. This is
+// actually keyed `attachment->filter`
 // @param {Object} env the current environment
 function addRules(current, definition, byFilter, env) {
     var newFilters = definition.filters,
@@ -296,7 +297,8 @@ function inheritDefinitions(definitions, env) {
     var inheritTime = +new Date();
     // definitions are ordered by specificity,
     // high (index 0) to low
-    var byAttachment = {}, byFilter = {};
+    var byAttachment = {},
+        byFilter = {};
     var result = [];
     var current, previous, attachment;
 
@@ -307,19 +309,22 @@ function inheritDefinitions(definitions, env) {
     });
 
     for (var i = 0; i < definitions.length; i++) {
+
         attachment = definitions[i].attachment;
         current = [definitions[i]];
+
         if (!byAttachment[attachment]) {
             byAttachment[attachment] = [];
             byAttachment[attachment].attachment = attachment;
             byFilter[attachment] = {};
             result.push(byAttachment[attachment]);
         }
+
         // Iterate over all subsequent rules.
         for (var j = i + 1; j < definitions.length; j++) {
             if (definitions[j].attachment === attachment) {
                 // Only inherit rules from the same attachment.
-                current = addRules(current, definitions[j], byFilter, env);
+                current = addRules(current, definitions[j], byFilter[attachment], env);
             }
         }
 
diff --git a/test/rendering-mss/issue_284.mss b/test/rendering-mss/issue_284.mss
index 05ed06b..e53218f 100644
--- a/test/rendering-mss/issue_284.mss
+++ b/test/rendering-mss/issue_284.mss
@@ -2,7 +2,7 @@
   [type='primary'] {
     line-color: red;
   }
-  [foo='bar'] { 
+  [foo='bar'] {
     line-width: 10;
   }
 }
@@ -14,4 +14,4 @@
   [foo='bar'] {
     line-width: 10;
   }
-}
\ No newline at end of file
+}
diff --git a/test/rendering-mss/issue_284.xml b/test/rendering-mss/issue_284.xml
index 0680115..8603ecc 100644
--- a/test/rendering-mss/issue_284.xml
+++ b/test/rendering-mss/issue_284.xml
@@ -1,4 +1,4 @@
-<Style name="style" filter-mode="first" >
+<Style name="style" filter-mode="first">
   <Rule>
     <Filter>([foo] = 'bar') and ([type] = 'primary')</Filter>
     <LineSymbolizer stroke-width="10" stroke="#ff0000" />
@@ -12,7 +12,7 @@
     <LineSymbolizer stroke="#ff0000" />
   </Rule>
 </Style>
-<Style name="style-outline" filter-mode="first" >
+<Style name="style-outline" filter-mode="first">
   <Rule>
     <Filter>([foo] = 'bar') and ([type] = 'primary')</Filter>
     <LineSymbolizer stroke-width="10" stroke="#ff0000" />