diff --git a/src/x11_monitor.c b/src/x11_monitor.c
index 3af827520..74c57ed01 100644
--- a/src/x11_monitor.c
+++ b/src/x11_monitor.c
@@ -151,6 +151,11 @@ void _glfwPollMonitorsX11(void)
             }
 
             XRRCrtcInfo* ci = XRRGetCrtcInfo(_glfw.x11.display, sr, oi->crtc);
+            if (!ci) {
+                XRRFreeOutputInfo(oi);
+                continue;
+            }
+
             if (ci->rotation == RR_Rotate_90 || ci->rotation == RR_Rotate_270)
             {
                 widthMM  = oi->mm_height;