diff --git a/src/main/java/com/github/dockerjava/core/command/BuildImageCmdImpl.java b/src/main/java/com/github/dockerjava/core/command/BuildImageCmdImpl.java
index 2bafce8c85..0384ba1457 100644
--- a/src/main/java/com/github/dockerjava/core/command/BuildImageCmdImpl.java
+++ b/src/main/java/com/github/dockerjava/core/command/BuildImageCmdImpl.java
@@ -327,7 +327,7 @@ public BuildImageCmdImpl withDockerfile(File dockerfile) {
             throw new IllegalArgumentException("Dockerfile does not exist");
         }
         if (!dockerfile.isFile()) {
-            throw new IllegalArgumentException("Not a directory");
+            throw new IllegalArgumentException("Dockerfile is not a file");
         }
 
         if (baseDirectory == null) {