diff --git a/libc/calls/ioctl.c b/libc/calls/ioctl.c
index 77d6141a3..21434d00e 100644
--- a/libc/calls/ioctl.c
+++ b/libc/calls/ioctl.c
@@ -106,10 +106,10 @@ static int ioctl_fionread(int fd, uint32_t *arg) {
       int bytes = CountConsoleInputBytes();
       *arg = MAX(0, bytes);
       return 0;
-    } else if (g_fds.p[fd].kind == kFdDevNull ||
-               g_fds.p[fd].kind == kFdDevRandom) {
-      *arg = 1;
-      return 0;
+    } else if (g_fds.p[fd].kind == kFdDevNull) {
+      return enotty();
+    } else if (g_fds.p[fd].kind == kFdDevRandom) {
+      return einval();
     } else if (GetFileType(handle) == kNtFileTypePipe) {
       uint32_t avail;
       if (PeekNamedPipe(handle, 0, 0, 0, &avail, 0)) {
diff --git a/libc/calls/write-nt.c b/libc/calls/write-nt.c
index 0e0aa4509..edea79f9f 100644
--- a/libc/calls/write-nt.c
+++ b/libc/calls/write-nt.c
@@ -52,9 +52,9 @@ static textwindows ssize_t sys_write_nt_impl(int fd, void *data, size_t size,
   struct Fd *f = g_fds.p + fd;
   bool isconsole = f->kind == kFdConsole;
 
-  // not implemented
+  // not implemented, XNU returns eperm();
   if (f->kind == kFdDevRandom) {
-    return enosys();
+    return eperm();
   }
 
   // determine win32 handle for writing
diff --git a/test/libc/calls/specialfile_test.c b/test/libc/calls/specialfile_test.c
index 17d0dac89..f96cea944 100644
--- a/test/libc/calls/specialfile_test.c
+++ b/test/libc/calls/specialfile_test.c
@@ -27,9 +27,12 @@
 
 int pipefd[2];
 int stdoutBack;
+int allowMask;
 
 void SetUpOnce(void) {
   testlib_enable_tmp_setup_teardown();
+  // qemu-aarch64 defines o_largefile wrong
+  allowMask = ~(O_LARGEFILE | 0x00008000);
 }
 
 void CaptureStdout(void) {
@@ -47,8 +50,7 @@ void RestoreStdout(void) {
 
 TEST(specialfile, devNull) {
   ASSERT_SYS(0, 3, creat("/dev/null", 0644));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
+  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & allowMask);
   ASSERT_SYS(0, 2, write(3, "hi", 2));
   ASSERT_SYS(0, 2, pwrite(3, "hi", 2, 0));
   ASSERT_SYS(0, 2, pwrite(3, "hi", 2, 2));
@@ -65,8 +67,7 @@ TEST(specialfile, devNull) {
 TEST(specialfile, devNullRead) {
   char buf[8] = {0};
   ASSERT_SYS(0, 3, open("/dev/null", O_RDONLY));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
+  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & allowMask);
   ASSERT_SYS(0, 0, read(3, buf, 8));
   ASSERT_SYS(0, 0, close(3));
 }
@@ -74,8 +75,7 @@ TEST(specialfile, devNullRead) {
 TEST(specialfile, devRandomRead) {
   char buf[8] = {0};
   ASSERT_SYS(0, 3, open("/dev/random", O_RDONLY));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
+  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & allowMask);
   ASSERT_SYS(0, 8, read(3, buf, 8));
   ASSERT_NE(0, memcmp(buf, "       ", 8));
   ASSERT_SYS(0, 0, close(3));
@@ -84,8 +84,7 @@ TEST(specialfile, devRandomRead) {
 TEST(specialfile, devUrandomRead) {
   char buf[8] = {0};
   ASSERT_SYS(0, 3, open("/dev/urandom", O_RDONLY));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
+  ASSERT_EQ(O_RDONLY, fcntl(3, F_GETFL) & allowMask);
   ASSERT_SYS(0, 8, read(3, buf, 8));
   ASSERT_NE(0, memcmp(buf, "       ", 8));
   ASSERT_SYS(0, 0, close(3));
@@ -97,9 +96,8 @@ TEST(specialfile, devRandomWrite_fails_on_nt) {
   }
   char buf[8] = {0};
   ASSERT_SYS(0, 3, creat("/dev/random", 0644));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
-  ASSERT_SYS(ENOSYS, -1, write(3, buf, 8));
+  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & allowMask);
+  ASSERT_SYS(EPERM, -1, write(3, buf, 8));
   ASSERT_SYS(0, 0, close(3));
 }
 
@@ -109,9 +107,8 @@ TEST(specialfile, devUrandomWrite_fails_on_nt) {
   }
   char buf[8] = {0};
   ASSERT_SYS(0, 3, creat("/dev/urandom", 0644));
-  // qemu-aarch64 defines o_largefile wrong
-  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & ~(O_LARGEFILE | 0x00008000));
-  ASSERT_SYS(ENOSYS, -1, write(3, buf, 8));
+  ASSERT_EQ(O_WRONLY, fcntl(3, F_GETFL) & allowMask);
+  ASSERT_SYS(EPERM, -1, write(3, buf, 8));
   ASSERT_SYS(0, 0, close(3));
 }