diff --git a/src/black/__init__.py b/src/black/__init__.py
index 3678067..94652ec 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -917,9 +917,6 @@ def format_file_contents(src_contents: str, *, fast: bool, mode: Mode) -> FileCo
     valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it.
     `mode` is passed to :func:`format_str`.
     """
-    if not mode.preview and not src_contents.strip():
-        raise NothingChanged
-
     if mode.is_ipynb:
         dst_contents = format_ipynb_string(src_contents, fast=fast, mode=mode)
     else:
@@ -1014,7 +1011,7 @@ def format_ipynb_string(src_contents: str, *, fast: bool, mode: Mode) -> FileCon
     Operate cell-by-cell, only on code cells, only for Python notebooks.
     If the ``.ipynb`` originally had a trailing newline, it'll be preserved.
     """
-    if mode.preview and not src_contents:
+    if not src_contents:
         raise NothingChanged
 
     trailing_newline = src_contents[-1] == "\n"
@@ -1109,7 +1106,7 @@ def _format_str_once(src_contents: str, *, mode: Mode) -> str:
     dst_contents = []
     for block in dst_blocks:
         dst_contents.extend(block.all_lines())
-    if mode.preview and not dst_contents:
+    if not dst_contents:
         # Use decode_bytes to retrieve the correct source newline (CRLF or LF),
         # and check if normalized_content has more than one line
         normalized_content, _, newline = decode_bytes(src_contents.encode("utf-8"))