diff --git a/src/main/org/apache/tools/ant/ProjectHelper.java b/src/main/org/apache/tools/ant/ProjectHelper.java
index d9b673930..0f462f471 100644
--- a/src/main/org/apache/tools/ant/ProjectHelper.java
+++ b/src/main/org/apache/tools/ant/ProjectHelper.java
@@ -233,10 +233,11 @@ public class ProjectHelper {
             if (project.getProperty("basedir") != null) {
                 project.setBasedir(project.getProperty("basedir"));
             } else {
+                String buildFileParent = (new File(buildFile.getAbsolutePath())).getParent();
                 if (baseDir == null) {
-                    project.setBasedir((new File(buildFile.getParent())).getAbsolutePath());
+                    project.setBasedir((new File(buildFileParent)).getAbsolutePath());
                 } else {
-                    project.setBasedir((new File(buildFile.getParent(), baseDir)).getAbsolutePath());
+                    project.setBasedir((new File(buildFileParent, baseDir)).getAbsolutePath());
                 }
             }