diff --git a/core/src/main/java/hudson/FilePath.java b/core/src/main/java/hudson/FilePath.java
index 587dbbf6f447..3ad30c4ac97c 100644
--- a/core/src/main/java/hudson/FilePath.java
+++ b/core/src/main/java/hudson/FilePath.java
@@ -3322,8 +3322,15 @@ public Boolean invoke(@Nonnull File parentFile, @Nonnull VirtualChannel channel)
             while (!remainingPath.isEmpty()) {
                 Path directChild = this.getDirectChild(currentFilePath, remainingPath);
                 Path childUsingFullPath = currentFilePath.resolve(remainingPath);
-                Path rel = directChild.toAbsolutePath().relativize(childUsingFullPath.toAbsolutePath());
-                remainingPath = rel.toString();
+                String childUsingFullPathAbs = childUsingFullPath.toAbsolutePath().toString();
+                String directChildAbs = directChild.toAbsolutePath().toString();
+
+                if (childUsingFullPathAbs.length() == directChildAbs.length()) {
+                    remainingPath = "";
+                } else {
+                    // +1 to avoid the last slash
+                    remainingPath = childUsingFullPathAbs.substring(directChildAbs.length() + 1);
+                }
 
                 File childFileSymbolic = Util.resolveSymlinkToFile(directChild.toFile());
                 if (childFileSymbolic == null) {
diff --git a/core/src/test/java/hudson/FilePathSEC904Test.java b/core/src/test/java/hudson/FilePathSEC904Test.java
index f72050de619e..a9b4d7afcc30 100644
--- a/core/src/test/java/hudson/FilePathSEC904Test.java
+++ b/core/src/test/java/hudson/FilePathSEC904Test.java
@@ -137,8 +137,12 @@ public void isDescendant_regularSymlinks() throws IOException, InterruptedExcept
         assertTrue(workspaceFolder.isDescendant("_nonexistent"));
         assertTrue(workspaceFolder.isDescendant("a"));
         assertTrue(workspaceFolder.isDescendant("a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("a/../a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b/../a/a.txt"));
         assertTrue(workspaceFolder.isDescendant("b"));
+        assertTrue(workspaceFolder.isDescendant("./b"));
         assertTrue(workspaceFolder.isDescendant("b/_a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b/_a/../a/a.txt"));
         assertTrue(workspaceFolder.isDescendant("b/_atxt"));
         
         // nonexistent but illegal
@@ -193,6 +197,12 @@ public void isDescendant_windowsSpecificSymlinks() throws Exception {
         
         assertTrue(workspaceFolder.isDescendant("b"));
         assertTrue(workspaceFolder.isDescendant("b/_a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b\\_a\\a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b\\_a\\../a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b\\_a\\..\\a\\a.txt"));
+        assertTrue(workspaceFolder.isDescendant(".\\b\\_a\\..\\a\\a.txt"));
+        assertTrue(workspaceFolder.isDescendant("b/_a/../a/a.txt"));
+        assertTrue(workspaceFolder.isDescendant("./b/_a/../a/a.txt"));
         
         // nonexistent and not proven illegal, the junction links are not resolved 
         // by Util.resolveSymlinkToFile / neither Path.toRealPath under Windows