diff --git a/src/fuse_init.cpp b/src/fuse_init.cpp
index ae6fcfb5..4a52771f 100644
--- a/src/fuse_init.cpp
+++ b/src/fuse_init.cpp
@@ -219,6 +219,7 @@ namespace FUSE
     l::spawn_thread_to_set_readahead();
 
     state.proc_self_fd_fd = open("/proc/self/fd",O_RDWR|O_PATH|O_DIRECTORY);
+    assert(state.proc_self_fd_fd != -1);
 
     return NULL;
   }