1 files changed, 2 insertions, 0 deletions

diff --git a/src/firejail/x11.c b/src/firejail/x11.c
index 49af2eff4..f1d45adef 100644
--- a/src/firejail/x11.c
+++ b/src/firejail/x11.c
@@ -568,6 +568,7 @@ void x11_start_xephyr(int argc, char **argv) {
                 (void) rv;
         }
 
+        assert(display_str);
         setenv("DISPLAY", display_str, 1);
         // run attach command
         jail = fork();
@@ -785,6 +786,7 @@ void x11_start_xpra(int argc, char **argv) {
                 _exit(1);
         }
 
+        assert(display_str);
         setenv("DISPLAY", display_str, 1);
 
         // build jail command