diff --git a/lfs.c b/lfs.c
index ec94fdc7..ac46d141 100644
--- a/lfs.c
+++ b/lfs.c
@@ -10659,11 +10659,12 @@ failed:;
 }
 
 int lfsr_file_flush(lfs_t *lfs, lfsr_file_t *file) {
-    // flushing readonly files is not supported
-    //
-    // in theory we could make this a noop, but that would be inconsistent
-    // with lfsr_file_sync
-    LFS_ASSERT(lfsr_o_iswriteable(file->flags));
+    // readonly files should do nothing
+    LFS_ASSERT(lfsr_o_iswriteable(file->flags)
+            || !lfsr_f_isunflushed(file->flags)
+            || (lfsr_file_size_(file) <= lfs->cfg->cache_size
+                && lfsr_file_size_(file) <= lfs->cfg->inline_size
+                && lfsr_file_size_(file) <= lfs->cfg->fragment_size));
 
     // do nothing if our file is already flushed
     if (!lfsr_f_isunflushed(file->flags)) {
@@ -10707,12 +10708,6 @@ failed:;
 }
 
 int lfsr_file_sync(lfs_t *lfs, lfsr_file_t *file) {
-    // syncing readonly files is not supported
-    //
-    // in theory we could make this a noop, but then syncing desynced
-    // readonly files would require disk writes
-    LFS_ASSERT(lfsr_o_iswriteable(file->flags));
-
     // do nothing if our file has been removed
     if (file->mdir.mid == -1) {
         return 0;
@@ -10751,6 +10746,21 @@ int lfsr_file_sync(lfs_t *lfs, lfsr_file_t *file) {
 
     // don't write to disk if our disk is already in-sync
     if (lfsr_f_isunsynced(file->flags)) {
+        // readonly files should do nothing
+        //
+        // but readonly files _can_ end up unsynced, in the roundabout
+        // case where:
+        //
+        // 1. a file is opened rdonly + desync
+        // 2. the same file is opened and written to
+        // 3. we try to sync our original file handle
+        //
+        // the best thing we can do in this case is return an error
+        if (!lfsr_o_iswriteable(file->flags)) {
+            err = LFS_ERR_INVAL;
+            goto failed;
+        }
+
         // checkpoint the allocator again
         lfs_alloc_ckpoint(lfs);
 
diff --git a/tests/test_fsync.toml b/tests/test_fsync.toml
index b6e583b1..60fa2e46 100644
--- a/tests/test_fsync.toml
+++ b/tests/test_fsync.toml
@@ -2085,6 +2085,107 @@ code = '''
     lfsr_unmount(&lfs) => 0;
 '''
 
+[cases.test_fsync_desync_wrrd_noop]
+code = '''
+    lfs_t lfs;
+    lfsr_format(&lfs, CFG) => 0;
+    lfsr_mount(&lfs, CFG) => 0;
+
+    // a - writer
+    // b - reader kept open, recvs updates from a
+    // c - desynced reader
+    lfsr_file_t a;
+    lfsr_file_t b;
+    lfsr_file_t c;
+    uint8_t rbuf[256];
+    lfsr_file_open(&lfs, &a, "jello",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_EXCL) => 0;
+    lfsr_file_open(&lfs, &b, "jello", LFS_O_RDONLY) => 0;
+    lfsr_file_open(&lfs, &c, "jello", LFS_O_RDONLY | LFS_O_DESYNC) => 0;
+
+    // write to a and sync
+    lfsr_file_write(&lfs, &a, "hello!", strlen("hello!"))
+            => strlen("hello!");
+    lfsr_file_sync(&lfs, &a) => 0;
+
+    // our write should show up in b
+    lfsr_file_read(&lfs, &b, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    // but not in c
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => 0;
+    // reopen c, should now be up to date
+    lfsr_file_close(&lfs, &c) => 0;
+    lfsr_file_open(&lfs, &c, "jello", LFS_O_RDONLY | LFS_O_DESYNC) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+
+    // rewrite a and sync
+    lfsr_file_rewind(&lfs, &a) => 0;
+    lfsr_file_write(&lfs, &a, "bonjour!", strlen("bonjour!"))
+            => strlen("bonjour!");
+    lfsr_file_sync(&lfs, &a) => 0;
+
+    // our write should show up in b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_read(&lfs, &b, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // but not in c
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+
+    // sync b, this should be a noop
+    lfsr_file_sync(&lfs, &b) => 0;
+
+    // our write should show up in b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_read(&lfs, &b, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // but not in c
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+
+    // as if things couldn't get weirder
+    //
+    // what do you think should happend if we sync c?
+    //
+    // in theory, this should update a + b + disk, but that would require
+    // writing to disk... instead we just error
+    lfsr_file_sync(&lfs, &c) => LFS_ERR_INVAL;
+
+    // our write should show up in b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_read(&lfs, &b, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // but not in c
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
+    assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
+    // reopen c, should now be up to date
+    lfsr_file_close(&lfs, &c) => 0;
+    lfsr_file_open(&lfs, &c, "jello", LFS_O_RDONLY | LFS_O_DESYNC) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+
+    // we _are_ allowed to sync c if it results in a noop
+    lfsr_file_sync(&lfs, &c) => 0;
+
+    // our write should show up in b
+    lfsr_file_rewind(&lfs, &b) => 0;
+    lfsr_file_read(&lfs, &b, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+    // and in c
+    lfsr_file_rewind(&lfs, &c) => 0;
+    lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
+    assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
+
+    lfsr_file_close(&lfs, &a) => 0;
+    lfsr_file_close(&lfs, &b) => 0;
+    lfsr_file_close(&lfs, &c) => 0;
+    lfsr_unmount(&lfs) => 0;
+'''
+
 [cases.test_fsync_desync_wdwdrr_append]
 code = '''
     lfs_t lfs;