diff --git a/lib/preprocessor.js b/lib/preprocessor.js
index cb5e424a1..64f918d96 100644
--- a/lib/preprocessor.js
+++ b/lib/preprocessor.js
@@ -39,6 +39,8 @@ var createPreprocessor = function (config, basePath, injector) {
 
       alreadyDisplayedWarnings[name] = true
     }
+
+    return instances[name]
   }
 
   patterns.forEach(function (pattern) {
@@ -80,9 +82,12 @@ var createPreprocessor = function (config, basePath, injector) {
             config[patterns[i]].join(', '), file.originalPath)
         } else {
           config[patterns[i]].forEach(function (name) {
-            if (!instances[name]) {
-              instantiatePreprocessor(name)
+            var p = instances[name] != null ? instances[name] : instantiatePreprocessor(name)
+
+            if (p == null) {
+              return log.warn('Could not instantiate perprocessor %s', name)
             }
+
             preprocessors.push(instances[name])
           })
         }