diff --git a/core/src/main/java/hudson/FilePath.java b/core/src/main/java/hudson/FilePath.java
index 81941cf6f78e7d00c7bfe75985ca4c94c544f232..564bb2763da49c16c3042ad48355a5d707858a29 100644
--- a/core/src/main/java/hudson/FilePath.java
+++ b/core/src/main/java/hudson/FilePath.java
@@ -294,6 +294,7 @@ public final class FilePath implements Serializable {
     public void unzip(FilePath target) throws IOException, InterruptedException {
         target.act(new FileCallable<Void>() {
             public Void invoke(File dir, VirtualChannel channel) throws IOException {
+                dir = dir.getAbsoluteFile();    // without absolutization, getParentFile below seems to fail
                 ZipInputStream zip = new ZipInputStream(FilePath.this.read());
                 java.util.zip.ZipEntry e;