diff --git a/plugin.gradle b/plugin.gradle
index d5f206c..81939bf 100644
--- a/plugin.gradle
+++ b/plugin.gradle
@@ -20,7 +20,7 @@ javascript {
         custom {
             js {
                 srcDir "src/test/resources"
-                include "*.js"
+                include "file*.js"
             }
         }
     }
@@ -39,6 +39,7 @@ task minify(type: com.eriwen.gradle.js.tasks.MinifyJsTask) {
     closure {
         warningLevel = 'VERBOSE'
         compilationLevel = 'SIMPLE_OPTIMIZATIONS'
+        externs = files("src/test/resources/externs.js")
     }
 }
 
diff --git a/src/main/groovy/com/eriwen/gradle/js/ClosureCompilerExtension.groovy b/src/main/groovy/com/eriwen/gradle/js/ClosureCompilerExtension.groovy
index 08d482d..645bacf 100644
--- a/src/main/groovy/com/eriwen/gradle/js/ClosureCompilerExtension.groovy
+++ b/src/main/groovy/com/eriwen/gradle/js/ClosureCompilerExtension.groovy
@@ -16,10 +16,12 @@
 package com.eriwen.gradle.js
 
 import com.google.javascript.jscomp.CompilerOptions
+import org.gradle.api.file.FileCollection
 
 class ClosureCompilerExtension {
     public static final NAME = "closure"
     CompilerOptions compilerOptions = new CompilerOptions()
     String compilationLevel = 'SIMPLE_OPTIMIZATIONS'
     String warningLevel = 'DEFAULT'
+    FileCollection externs = null
 }
diff --git a/src/main/groovy/com/eriwen/gradle/js/JsMinifier.groovy b/src/main/groovy/com/eriwen/gradle/js/JsMinifier.groovy
index 01a45aa..d7ade3e 100644
--- a/src/main/groovy/com/eriwen/gradle/js/JsMinifier.groovy
+++ b/src/main/groovy/com/eriwen/gradle/js/JsMinifier.groovy
@@ -7,6 +7,8 @@ import com.google.javascript.jscomp.CompilerOptions
 import com.google.javascript.jscomp.JSSourceFile
 import com.google.javascript.jscomp.Result
 import com.google.javascript.jscomp.WarningLevel
+import java.nio.charset.Charset
+import org.gradle.api.file.FileCollection
 
 /**
  * Util to minify JS files with Google Closure Compiler.
@@ -16,23 +18,25 @@ import com.google.javascript.jscomp.WarningLevel
  */
 class JsMinifier {
 
-
-    void minifyJsFile(final File inputFile, final File outputFile, final CompilerOptions options,
+    void minifyJsFile(final File inputFile, final Set<File> externsFiles, final File outputFile, final CompilerOptions options,
             final String warningLevel, final String compilationLevel) {
-		Compiler compiler = new Compiler()
-		CompilationLevel.valueOf(compilationLevel).setOptionsForCompilationLevel(options)
-		WarningLevel level = WarningLevel.valueOf(warningLevel)
-		level.setOptionsForWarningLevel(options)
-		List<JSSourceFile> externs = CommandLineRunner.getDefaultExterns()
+        Compiler compiler = new Compiler()
+        CompilationLevel.valueOf(compilationLevel).setOptionsForCompilationLevel(options)
+        WarningLevel level = WarningLevel.valueOf(warningLevel)
+        level.setOptionsForWarningLevel(options)
+        List<JSSourceFile> externs = CommandLineRunner.getDefaultExterns()
+        if (externsFiles.size()) {
+            externs.addAll(externsFiles.collect() { JSSourceFile.fromFile(it) })
+        }
         List<JSSourceFile> inputs = new ArrayList<JSSourceFile>()
         inputs.add(JSSourceFile.fromFile(inputFile))
-		Result result = compiler.compile(externs, inputs, options)
-		if (result.success) {
-			outputFile.write(compiler.toSource())
-		} else {
-			result.errors.each {
-				println "${it.sourceName}:${it.lineNumber} - ${it.description}"
-			}
-		}
+        Result result = compiler.compile(externs, inputs, options)
+        if (result.success) {
+            outputFile.write(compiler.toSource())
+        } else {
+            result.errors.each {
+                println "${it.sourceName}:${it.lineNumber} - ${it.description}"
+            }
+        }
     }
 }
diff --git a/src/main/groovy/com/eriwen/gradle/js/tasks/MinifyJsTask.groovy b/src/main/groovy/com/eriwen/gradle/js/tasks/MinifyJsTask.groovy
index 03faed6..1f75b29 100644
--- a/src/main/groovy/com/eriwen/gradle/js/tasks/MinifyJsTask.groovy
+++ b/src/main/groovy/com/eriwen/gradle/js/tasks/MinifyJsTask.groovy
@@ -34,6 +34,8 @@ class MinifyJsTask extends SourceTask {
             throw new GradleException("Only 1 file can be minified. Please run MinifyJs for each file.")
         }
 
-        MINIFIER.minifyJsFile((source.files.toArray() as File[])[0], dest, project.closure.compilerOptions, project.closure.warningLevel, project.closure.compilationLevel)
+        Set<File> externsFiles = project.closure.externs ? project.closure.externs.files : [] as Set<File>
+        MINIFIER.minifyJsFile((source.files.toArray() as File[])[0], externsFiles, dest,
+                project.closure.compilerOptions, project.closure.warningLevel, project.closure.compilationLevel)
     }
 }
diff --git a/src/test/resources/externs.js b/src/test/resources/externs.js
new file mode 100644
index 0000000..95d5d85
--- /dev/null
+++ b/src/test/resources/externs.js
@@ -0,0 +1 @@
+var console = {};
diff --git a/src/test/resources/file1.js b/src/test/resources/file1.js
index 6f75907..c105981 100644
--- a/src/test/resources/file1.js
+++ b/src/test/resources/file1.js
@@ -5,4 +5,4 @@
 function test1() {
     console.log('test1');
     return true;
-}
\ No newline at end of file
+}