diff --git a/pkgs/development/python-modules/stringzilla/default.nix b/pkgs/development/python-modules/stringzilla/default.nix
index 05edc2fdf6c5..35876032eea4 100644
--- a/pkgs/development/python-modules/stringzilla/default.nix
+++ b/pkgs/development/python-modules/stringzilla/default.nix
@@ -21,6 +21,10 @@ buildPythonPackage rec {
     hash = "sha256-0CIekVxChvH912vFnBF2FR1YyIpxi3SD7KhBlh7yFGA=";
   };
 
+  # Define _POSIX_C_SOURCE to enable POSIX signal handling for ARM capability detection
+  # See: https://github.com/ashvardanian/StringZilla/pull/263
+  env.NIX_CFLAGS_COMPILE = "-D_POSIX_C_SOURCE=200809L";
+
   postPatch = lib.optionalString stdenv.hostPlatform.isDarwin ''
     # error: unsupported option '-mfloat-abi=' for target 'aarch64-apple-darwin'
     substituteInPlace setup.py \