Grab keyboard/mouse not possible on xcb plugin

diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index 3818494..6369cbe 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -165,7 +165,7 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
                "\t Use the -dograb option to enforce grabbing.");
     }
 #endif
-    m_canGrab = (!underDebugger && noGrabArg) || (underDebugger && doGrabArg);
+    m_canGrab = (!underDebugger && noGrabArg) || (underDebugger && doGrabArg) || (!underDebugger && !noGrabArg && !doGrabArg);
 
     static bool canNotGrabEnv = qEnvironmentVariableIsSet("QT_XCB_NO_GRAB_SERVER");
     if (canNotGrabEnv)