diff --git a/include/asterisk/module.h b/include/asterisk/module.h
index cce8735fc1..f79dc8eb10 100644
--- a/include/asterisk/module.h
+++ b/include/asterisk/module.h
@@ -283,7 +283,7 @@ int ast_loader_unregister(int (*updater)(void));
  * \param type The type of action that will be performed by CLI.
  *
  * \retval A possible completion of the partial match.
- * \retval NULL if no matches were found.
+ * \retval NULL if no matches were found or Asterisk is not yet fully booted.
  */
 char *ast_module_helper(const char *line, const char *word, int pos, int state, int rpos, enum ast_module_helper_type type);
 
diff --git a/main/loader.c b/main/loader.c
index 4c6c2a809e..549e3f0e52 100644
--- a/main/loader.c
+++ b/main/loader.c
@@ -1382,6 +1382,11 @@ char *ast_module_helper(const char *line, const char *word, int pos, int state,
 		return NULL;
 	}
 
+	/* Tab completion can't be used during startup, or CLI and loader will deadlock. */
+	if (!ast_test_flag(&ast_options, AST_OPT_FLAG_FULLY_BOOTED)) {
+		return NULL;
+	}
+
 	if (type == AST_MODULE_HELPER_LOAD) {
 		module_load_helper(word);