diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c
index 8950137c20..2b497b3529 100644
--- a/src/or/connection_edge.c
+++ b/src/or/connection_edge.c
@@ -1398,6 +1398,9 @@ connection_ap_make_bridge(char *address, uint16_t port)
     return -1;
   }
 
+  tor_assert(fd[0] >= 0);
+  tor_assert(fd[1] >= 0);
+
   set_socket_nonblocking(fd[0]);
   set_socket_nonblocking(fd[1]);
 
diff --git a/src/or/cpuworker.c b/src/or/cpuworker.c
index badca3563e..29fd992f62 100644
--- a/src/or/cpuworker.c
+++ b/src/or/cpuworker.c
@@ -329,6 +329,9 @@ spawn_cpuworker(void)
     return -1;
   }
 
+  tor_assert(fdarray[0] >= 0);
+  tor_assert(fdarray[1] >= 0);
+
   fd = fdarray[0];
   spawn_func(cpuworker_main, (void*)fdarray);
   log_debug(LD_OR,"just spawned a cpu worker.");
diff --git a/src/or/dns.c b/src/or/dns.c
index 79b4acceda..2d3d800c29 100644
--- a/src/or/dns.c
+++ b/src/or/dns.c
@@ -941,6 +941,9 @@ spawn_dnsworker(void)
     return -1;
   }
 
+  tor_assert(fdarray[0] >= 0);
+  tor_assert(fdarray[1] >= 0);
+
   /* log_fn(LOG_NOTICE,"Before spawn: fdarray @%d has %d:%d",
             (int)fdarray, fdarray[0],fdarray[1]); */