diff --git a/lib/carto/tree/color.js b/lib/carto/tree/color.js
index b052cde..fbdb41c 100644
--- a/lib/carto/tree/color.js
+++ b/lib/carto/tree/color.js
@@ -19,7 +19,7 @@ tree.Color = function Color(rgb, a) {
         });
     }
 
-    if (typeof(a) === 'Number') {
+    if (typeof(a) === 'number') {
         this.alpha = a;
     } else if (rgb.length === 4) {
         this.alpha = rgb[3];
diff --git a/test/rendering/fadeout.mml b/test/rendering/fadeout.mml
new file mode 100644
index 0000000..8bd0d62
--- /dev/null
+++ b/test/rendering/fadeout.mml
@@ -0,0 +1,14 @@
+{
+    "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+    "Stylesheet": [
+        "fadeout.mss"
+    ],
+    "Layer": [{
+        "name": "world",
+        "srs": "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over",
+        "Datasource": {
+            "file": "http://tilemill-data.s3.amazonaws.com/test_data/shape_demo.zip",
+            "type": "shape"
+        }
+    }]
+}
diff --git a/test/rendering/fadeout.mss b/test/rendering/fadeout.mss
new file mode 100644
index 0000000..2c74fc7
--- /dev/null
+++ b/test/rendering/fadeout.mss
@@ -0,0 +1,3 @@
+#world {
+    marker-fill: fadeout(#000, 5j);
+}
diff --git a/test/rendering/fadeout.result b/test/rendering/fadeout.result
new file mode 100644
index 0000000..53e9633
--- /dev/null
+++ b/test/rendering/fadeout.result
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE Map[]>
+<Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" maximum-extent="-20037508.34,-20037508.34,20037508.34,20037508.34">
+
+
+<Style name="world" filter-mode="first">
+  <Rule>
+    <MarkersSymbolizer fill="rgba(0, 0, 0, 0.5)" />
+  </Rule>
+</Style>
+<Layer name="world"
+  srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over">
+    <StyleName>world</StyleName>
+    <Datasource>
+       <Parameter name="file"><![CDATA[[absolute path]]]></Parameter>
+       <Parameter name="type"><![CDATA[shape]]></Parameter>
+    </Datasource>
+  </Layer>
+
+</Map>