diff --git a/WHATSNEW b/WHATSNEW
index 826f7e47f..b11d089aa 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -161,6 +161,11 @@ Fixed bugs:
    make the exit codes work in environments where 4NT or MKS are installed
    Bugzilla Report 41039.
 
+ * <signjar> would fail if used via its Java API and the File passed
+   into the setJar method was not "normalized" (i.e. contained ".."
+   segments).
+   Bugzilla Report 50081
+
 Other changes:
 --------------
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/Move.java b/src/main/org/apache/tools/ant/taskdefs/Move.java
index 358654fcc..9b01c4093 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Move.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Move.java
@@ -355,7 +355,7 @@ public class Move extends Copy {
                     + " is a no-op.", Project.MSG_VERBOSE);
                 return true;
             }
-            if (!(sourceFile.equals(destFile.getCanonicalFile()) || destFile.delete())) {
+            if (!(getFileUtils().areSame(sourceFile, destFile) || destFile.delete())) {
                 throw new BuildException("Unable to remove existing file " + destFile);
             }
         }
diff --git a/src/main/org/apache/tools/ant/taskdefs/SignJar.java b/src/main/org/apache/tools/ant/taskdefs/SignJar.java
index 67a4a37e0..3523f35c8 100644
--- a/src/main/org/apache/tools/ant/taskdefs/SignJar.java
+++ b/src/main/org/apache/tools/ant/taskdefs/SignJar.java
@@ -378,7 +378,7 @@ public class SignJar extends AbstractJarSignerTask {
      * @throws BuildException
      */
     private void signOneJar(File jarSource, File jarTarget)
-            throws BuildException {
+        throws BuildException {
 
 
         File targetFile = jarTarget;
@@ -401,12 +401,16 @@ public class SignJar extends AbstractJarSignerTask {
             addValue(cmd, value);
         }
 
+        try {
         //DO NOT SET THE -signedjar OPTION if source==dest
         //unless you like fielding hotspot crash reports
-        if (!jarSource.equals(targetFile)) {
+        if (!FILE_UTILS.areSame(jarSource, targetFile)) {
             addValue(cmd, "-signedjar");
             addValue(cmd, targetFile.getPath());
         }
+        } catch (IOException ioex) {
+            throw new BuildException(ioex);
+        }
 
         if (internalsf) {
             addValue(cmd, "-internalsf");
diff --git a/src/main/org/apache/tools/ant/util/FileUtils.java b/src/main/org/apache/tools/ant/util/FileUtils.java
index 38b82f9dc..073d98b62 100644
--- a/src/main/org/apache/tools/ant/util/FileUtils.java
+++ b/src/main/org/apache/tools/ant/util/FileUtils.java
@@ -1256,6 +1256,25 @@ public class FileUtils {
                 normalize(f2.getAbsolutePath()).getAbsolutePath());
     }
 
+    /**
+     * Are the two File instances pointing to the same object on the
+     * file system?
+     * @since Ant 1.8.2
+     */
+    public boolean areSame(File f1, File f2) throws IOException {
+        if (f1 == null && f2 == null) {
+            return true;
+        }
+        if (f1 == null || f2 == null) {
+            return false;
+        }
+        File f1Normalized = normalize(f1.getAbsolutePath());
+        File f2Normalized = normalize(f2.getAbsolutePath());
+        return f1Normalized.equals(f2Normalized)
+            || f1Normalized.getCanonicalFile().equals(f2Normalized
+                                                      .getCanonicalFile());
+    }
+
     /**
      * Renames a file, even if that involves crossing file system boundaries.
      *
@@ -1285,8 +1304,7 @@ public class FileUtils {
             System.err.println("Rename of " + from + " to " + to + " is a no-op.");
             return;
         }
-        if (to.exists() &&
-            !(from.equals(to.getCanonicalFile()) || tryHardToDelete(to))) {
+        if (to.exists() && !(areSame(from, to) || tryHardToDelete(to))) {
             throw new IOException("Failed to delete " + to + " while trying to rename " + from);
         }
         File parent = to.getParentFile();
diff --git a/src/tests/junit/org/apache/tools/ant/taskdefs/SignJarTest.java b/src/tests/junit/org/apache/tools/ant/taskdefs/SignJarTest.java
index 7b819c1da..7c810beef 100644
--- a/src/tests/junit/org/apache/tools/ant/taskdefs/SignJarTest.java
+++ b/src/tests/junit/org/apache/tools/ant/taskdefs/SignJarTest.java
@@ -106,4 +106,24 @@ public class SignJarTest extends BuildFileTest {
         }
     }
 
+    /**
+     * @see https://issues.apache.org/bugzilla/show_bug.cgi?id=50081
+     */
+    public void testSignUnnormalizedJar() throws Exception {
+        executeTarget("jar");
+        File testJar = new File(getProject().getProperty("test.jar"));
+        File testJarParent = testJar.getParentFile();
+        File f = new File(testJarParent,
+                          "../" + testJarParent.getName() + "/"
+                          + testJar.getName());
+        assertFalse(testJar.equals(f));
+        assertEquals(testJar.getCanonicalPath(), f.getCanonicalPath());
+        SignJar s = new SignJar();
+        s.setProject(getProject());
+        s.setJar(f);
+        s.setAlias("testonly");
+        s.setStorepass("apacheant");
+        s.setKeystore("testkeystore");
+        s.execute();
+    }
 }