diff --git a/asdf/_asdf.py b/asdf/_asdf.py
index b09b4f8d1..1691f2783 100644
--- a/asdf/_asdf.py
+++ b/asdf/_asdf.py
@@ -1070,9 +1070,9 @@ def update(
             def rewrite():
                 self._fd.seek(0)
                 self._serial_write(self._fd, pad_blocks, include_block_index)
+                self._fd.truncate()
                 if self._fd.can_memmap():
                     self._fd.close_memmap()
-                self._fd.truncate()
 
             # if we have no read blocks, we can just call write_to as no internal blocks are reused
             if len(self._blocks.blocks) == 0:
@@ -1107,9 +1107,9 @@ def rewrite():
 
                 # close memmap to trigger arrays to reload themselves
                 self._fd.seek(end_of_file)
+                self._fd.truncate()
                 if self._fd.can_memmap():
                     self._fd.close_memmap()
-                self._fd.truncate()
 
             finally:
                 self._post_write(fd)
diff --git a/asdf/generic_io.py b/asdf/generic_io.py
index 76a3b9157..5edc6b44d 100644
--- a/asdf/generic_io.py
+++ b/asdf/generic_io.py
@@ -738,9 +738,6 @@ def fast_forward(self, size):
         self.seek(size, SEEK_CUR)
 
     def truncate(self, size=None):
-        # windows supports truncating as long as the file not opened
-        # more than once. So this must be called after closing all
-        # memmaps
         if size is None:
             self._fd.truncate()
         else:
@@ -837,6 +834,15 @@ def close(self):
         if self._close:
             self._fix_permissions()
 
+    def truncate(self, size=None):
+        # windows supports truncating as long as the file not opened
+        # more than once. So this must be called after closing all
+        # memmaps
+        if sys.platform.startswith("win") and hasattr(self, "_mmap"):
+            self._mmap.close()
+            self.close_memmap()
+        super().truncate(size=size)
+
 
 class MemoryIO(RandomAccessFile):
     """