diff --git a/build.gradle b/build.gradle
index 05d7b68..4af5d7a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -32,12 +32,12 @@ java {
 }
 
 dependencies {
-
     compileOnly  "org.embulk:embulk-spi:0.11"
     implementation "org.embulk:embulk-util-config:0.5.0"
     implementation "org.embulk:embulk-util-file:0.2.0"
 
     testImplementation "junit:junit:4.13.2"
+    testImplementation "org.embulk:embulk-core:0.11.3"
     testImplementation "org.embulk:embulk-deps:0.11.3"
     testImplementation "org.embulk:embulk-junit4:0.11.3"
 }
diff --git a/src/main/java/org/embulk/input/CommandFileInputPlugin.java b/src/main/java/org/embulk/input/CommandFileInputPlugin.java
index 4022d4d..e95aaf5 100644
--- a/src/main/java/org/embulk/input/CommandFileInputPlugin.java
+++ b/src/main/java/org/embulk/input/CommandFileInputPlugin.java
@@ -126,7 +126,7 @@ public TransactionalFileInput open(TaskSource taskSource, int taskIndex)
         }
     }
 
-    protected static List<String> buildShell()
+    static List<String> buildShell()
     {
         String osName = System.getProperty("os.name");
         if(osName.indexOf("Windows") >= 0) {