diff --git a/lru-cache.js b/lru-cache.js
index b68021f..a5cbcad 100644
--- a/lru-cache.js
+++ b/lru-cache.js
@@ -63,8 +63,8 @@ Cache.prototype = {
       return Math.max(0, (this.order.length - this.size));
     } else if (this.type === typeEnum.heap) {
       if (getHeapSize() >= this.size) {
-        // Remove a quarter of them.
-        return (this.order.length >> 2);
+        // Remove half of them.
+        return (this.order.length >> 1);
       } else { return 0; }
     } else {
       console.error("Unknown heuristic for LRU cache.");
diff --git a/server.js b/server.js
index 5db7e7f..b53c41b 100644
--- a/server.js
+++ b/server.js
@@ -147,8 +147,8 @@ var minAccuracy = 0.75;
 //       = 1 - max(1, df) / rf
 var freqRatioMax = 1 - minAccuracy;
 
-// Request cache size of 500MB heap limit.
-var requestCache = new LruCache(500000000, 'heap');
+// Request cache size of 400MB heap limit.
+var requestCache = new LruCache(400000000, 'heap');
 
 // Deep error handling for vendor hooks.
 var vendorDomain = domain.create();
@@ -219,11 +219,13 @@ function cache(f) {
         options = uri;
       }
       return request(options, function(err, res, json) {
-        var cacheControl = res.headers['cache-control'];
-        if (cacheControl != null) {
-          var age = cacheControl.match(/max-age=([0-9]+)/);
-          if ((age != null) && (+age[1] === +age[1])) {
-            cacheInterval = +age[1] * 1000;
+        if (res != null && res.headers != null) {
+          var cacheControl = res.headers['cache-control'];
+          if (cacheControl != null) {
+            var age = cacheControl.match(/max-age=([0-9]+)/);
+            if ((age != null) && (+age[1] === +age[1])) {
+              cacheInterval = +age[1] * 1000;
+            }
           }
         }
         callback(err, res, json);