diff --git a/src/corelib/io/qstandardpaths_unix.cpp b/src/corelib/io/qstandardpaths_unix.cpp
index 3fb36589d26..932ae6b6ccb 100644
--- a/src/corelib/io/qstandardpaths_unix.cpp
+++ b/src/corelib/io/qstandardpaths_unix.cpp
@@ -127,6 +127,7 @@ QString QStandardPaths::writableLocation(StandardLocation type)
                     return QString();
                 }
             }
+            qWarning("QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '%s'", qPrintable(xdgRuntimeDir));
         }
         // "The directory MUST be owned by the user"
         QFileInfo fileInfo(xdgRuntimeDir);