diff --git a/chb/buffer/LibraryCallCallsites.py b/chb/buffer/LibraryCallCallsites.py
index 6847fa40..cbb7219c 100644
--- a/chb/buffer/LibraryCallCallsites.py
+++ b/chb/buffer/LibraryCallCallsites.py
@@ -358,7 +358,8 @@ def known_input_length(self) -> Optional[str]:
             fmtarg = self.instr.call_arguments[1]
             if fmtarg.is_string_reference:
                 fmtstr = (cast(XprConstant, fmtarg)).constant.string_reference()
-                if not "%s" in fmtstr:
+                # TODO: Smarter heuristics for problematic length fmt strings
+                if not "%" in fmtstr:
                     return "sprintf:max_length_fmt"
                 else:
                     return None
@@ -368,7 +369,8 @@ def known_input_length(self) -> Optional[str]:
             fmtarg = self.instr.call_arguments[2]
             if fmtarg.is_string_reference:
                 fmtstr = (cast(XprConstant, fmtarg)).constant.string_reference()
-                if not "%s" in fmtstr:
+                # TODO: Smarter heuristics for problematic length fmt strings
+                if not "%" in fmtstr:
                     return "snprintf:max_length_fmt"
                 else:
                     return None