diff --git a/Tests/images/crash-5762152299364352.fli b/Tests/images/crash-5762152299364352.fli
index 944fe0b56..d7588eea8 100644
Binary files a/Tests/images/crash-5762152299364352.fli and b/Tests/images/crash-5762152299364352.fli differ
diff --git a/Tests/images/timeout-9139147ce93e20eb14088fe238e541443ffd64b3.fli b/Tests/images/timeout-9139147ce93e20eb14088fe238e541443ffd64b3.fli
index ce4607d2d..73da81dcb 100644
Binary files a/Tests/images/timeout-9139147ce93e20eb14088fe238e541443ffd64b3.fli and b/Tests/images/timeout-9139147ce93e20eb14088fe238e541443ffd64b3.fli differ
diff --git a/Tests/images/timeout-bff0a9dc7243a8e6ede2408d2ffa6a9964698b87.fli b/Tests/images/timeout-bff0a9dc7243a8e6ede2408d2ffa6a9964698b87.fli
index 77a94b87a..abe642e6a 100644
Binary files a/Tests/images/timeout-bff0a9dc7243a8e6ede2408d2ffa6a9964698b87.fli and b/Tests/images/timeout-bff0a9dc7243a8e6ede2408d2ffa6a9964698b87.fli differ
diff --git a/src/PIL/FliImagePlugin.py b/src/PIL/FliImagePlugin.py
index ccb8a5953..c8e38f6be 100644
--- a/src/PIL/FliImagePlugin.py
+++ b/src/PIL/FliImagePlugin.py
@@ -49,7 +49,12 @@ class FliImageFile(ImageFile.ImageFile):
     def _open(self) -> None:
         # HEAD
         s = self.fp.read(128)
-        if not (_accept(s) and s[20:22] == b"\x00\x00"):
+        if not (
+            _accept(s)
+            and s[20:22] == b"\x00" * 2
+            and s[42:80] == b"\x00" * 38
+            and s[88:] == b"\x00" * 40
+        ):
             msg = "not an FLI/FLC file"
             raise SyntaxError(msg)