Index: /applications/editors/josm/plugins/ext_tools/src/ext_tools/ExtTool.java
===================================================================
--- /applications/editors/josm/plugins/ext_tools/src/ext_tools/ExtTool.java	(revision 32687)
+++ /applications/editors/josm/plugins/ext_tools/src/ext_tools/ExtTool.java	(revision 32688)
@@ -9,4 +9,5 @@
 import java.io.InputStream;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
@@ -204,5 +205,5 @@
                 showErrorMessage(
                         tr("Error executing the script:"),
-                        debugstr.toString() + e.getMessage() + "\n" + e.getStackTrace());
+                        debugstr.toString() + e.getMessage() + "\n" + Arrays.toString(e.getStackTrace()));
             }
             return;