diff --git a/src/nvim/eval/fs.c b/src/nvim/eval/fs.c
index c5e0898ef8..c993f0d371 100644
--- a/src/nvim/eval/fs.c
+++ b/src/nvim/eval/fs.c
@@ -1733,13 +1733,13 @@ write_blob_error:
 }
 
 static bool write_blob(FileDescriptor *const fp, const blob_T *const blob)
-  FUNC_ATTR_NONNULL_ARG(1)
+  FUNC_ATTR_NONNULL_ALL
 {
   return write_data(fp, blob->bv_ga.ga_data, (size_t)tv_blob_len(blob));
 }
 
 static bool write_string(FileDescriptor *const fp, const char *const data)
-  FUNC_ATTR_NONNULL_ARG(1)
+  FUNC_ATTR_NONNULL_ALL
 {
   return write_data(fp, data, strlen(data));
 }
@@ -1833,7 +1833,7 @@ void f_writefile(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
     bool write_ok;
     if (argvars[0].v_type == VAR_BLOB) {
-      write_ok = write_blob(&fp, argvars[0].vval.v_blob);
+      write_ok = argvars[0].vval.v_blob == NULL || write_blob(&fp, argvars[0].vval.v_blob);
     } else if (argvars[0].v_type == VAR_STRING) {
       write_ok = write_string(&fp, argvars[0].vval.v_string);
     } else {
diff --git a/test/functional/vimscript/writefile_spec.lua b/test/functional/vimscript/writefile_spec.lua
index f406e5a469..b784868a7b 100644
--- a/test/functional/vimscript/writefile_spec.lua
+++ b/test/functional/vimscript/writefile_spec.lua
@@ -65,6 +65,13 @@ describe('writefile()', function()
     eq('\n', read_file(fname))
   end)
 
+  it('writes a null blob to a file', function()
+    eq(0, fn.writefile({ 'line1' }, fname, 'b'))
+    eq('line1', read_file(fname))
+    command(('call writefile(v:_null_blob, "%s")'):format(fname))
+    eq('', read_file(fname))
+  end)
+
   it('appends to a file', function()
     eq(nil, read_file(fname))
     eq(0, fn.writefile({ 'abc', 'def', 'ghi' }, fname))
@@ -100,7 +107,7 @@ describe('writefile()', function()
     eq('a\0', read_file(fname))
   end)
 
-  it('writes Lua strings to a file', function()
+  it('writes Lua (binary) strings to a file', function()
     eq(0, exec_lua([[return vim.fn.writefile('foo\0bar', ..., 'b')]], fname))
     eq('foo\0bar', read_file(fname))
   end)