diff --git a/sandboxed_api/sandbox2/forkserver.cc b/sandboxed_api/sandbox2/forkserver.cc
index afbef40..ab16ee7 100644
--- a/sandboxed_api/sandbox2/forkserver.cc
+++ b/sandboxed_api/sandbox2/forkserver.cc
@@ -189,6 +189,7 @@ pid_t ForkClient::SendRequest(const ForkRequest& request, int exec_fd,
     SAPI_RAW_LOG(ERROR, "Sending PB to the ForkServer failed");
     return -1;
   }
+  SAPI_RAW_CHECK(comms_fd != -1, "comms_fd was not properly set up");
   if (!comms_->SendFD(comms_fd)) {
     SAPI_RAW_LOG(ERROR, "Sending Comms FD (%d) to the ForkServer failed",
                  comms_fd);
@@ -196,6 +197,7 @@ pid_t ForkClient::SendRequest(const ForkRequest& request, int exec_fd,
   }
   if (request.mode() == FORKSERVER_FORK_EXECVE ||
       request.mode() == FORKSERVER_FORK_EXECVE_SANDBOX) {
+    SAPI_RAW_CHECK(exec_fd != -1, "exec_fd cannot be -1 in execve mode");
     if (!comms_->SendFD(exec_fd)) {
       SAPI_RAW_LOG(ERROR, "Sending Exec FD (%d) to the ForkServer failed",
                    exec_fd);
@@ -204,6 +206,7 @@ pid_t ForkClient::SendRequest(const ForkRequest& request, int exec_fd,
   }
 
   if (request.mode() == FORKSERVER_FORK_JOIN_SANDBOX_UNWIND) {
+    SAPI_RAW_CHECK(user_ns_fd != -1, "user_ns_fd cannot be -1 in unwind mode");
     if (!comms_->SendFD(user_ns_fd)) {
       SAPI_RAW_LOG(ERROR, "Sending user ns FD (%d) to the ForkServer failed",
                    user_ns_fd);
diff --git a/sandboxed_api/sandbox2/forkserver_test.cc b/sandboxed_api/sandbox2/forkserver_test.cc
index 6cc87f8..3750a3e 100644
--- a/sandboxed_api/sandbox2/forkserver_test.cc
+++ b/sandboxed_api/sandbox2/forkserver_test.cc
@@ -104,19 +104,6 @@ TEST(ForkserverTest, ForkExecveSandboxWithoutPolicy) {
   // Run a test binary through the FORKSERVER_FORK_EXECVE_SANDBOX request.
   int exec_fd = GetMinimalTestcaseFd();
   PCHECK(exec_fd != -1) << "Could not open test binary";
-  ASSERT_NE(TestSingleRequest(FORKSERVER_FORK_EXECVE_SANDBOX, exec_fd, -1), -1);
-}
-
-TEST(ForkserverTest, ForkExecveRequiresExecFD) {
-  // This test should generate some warnings:
-  // (Sending Exec FD (-1) to the ForkServer failed).
-  ASSERT_EQ(TestSingleRequest(FORKSERVER_FORK_EXECVE, -1, -1), -1);
-}
-
-TEST(ForkserverTest, ForkExecveSandboxRequiresExecFD) {
-  // This test should generate some warnings:
-  // (Sending Exec FD (-1) to the ForkServer failed).
-  ASSERT_EQ(TestSingleRequest(FORKSERVER_FORK_EXECVE_SANDBOX, -1, -1), -1);
 }
 
 }  // namespace sandbox2