diff --git a/src/main.c b/src/main.c
index 2458377..788309d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -39,6 +39,7 @@ static int caught_signal = 0;
 #define DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER 1
 #define DBUS_REQUEST_NAME_REPLY_ALREADY_OWNER 4
 
+#define DEFAULT_SHELL_DEBUG SHELL_DEBUG_BACKTRACE_SEGFAULTS
 enum {
   SHELL_DEBUG_BACKTRACE_WARNINGS = 1,
   SHELL_DEBUG_BACKTRACE_SEGFAULTS = 2,
@@ -268,8 +269,11 @@ shell_init_debug (const char *debug_env)
     { "backtrace-segfaults", SHELL_DEBUG_BACKTRACE_SEGFAULTS },
   };
 
-  _shell_debug = g_parse_debug_string (debug_env, keys,
-                                       G_N_ELEMENTS (keys));
+  if (debug_env)
+    _shell_debug = g_parse_debug_string (debug_env, keys,
+                                         G_N_ELEMENTS (keys));
+  else
+    _shell_debug = DEFAULT_SHELL_DEBUG;
 }
 
 static void