diff --git a/pkgs/by-name/lc/lcalc/package.nix b/pkgs/by-name/lc/lcalc/package.nix
index f81ea501270fc..22f326219a475 100644
--- a/pkgs/by-name/lc/lcalc/package.nix
+++ b/pkgs/by-name/lc/lcalc/package.nix
@@ -19,6 +19,14 @@ stdenv.mkDerivation rec {
     hash = "sha256-RxWZ7T0I9zV7jUVnL6jV/PxEoU32KY7Q1UsOL5Lonuc=";
   };
 
+  # workaround for vendored GCC 3.5 <complex>
+  # https://gitlab.com/sagemath/lcalc/-/issues/16
+  env.NIX_CFLAGS_COMPILE = toString [
+    "-D_GLIBCXX_COMPLEX"
+    "-D_LIBCPP_COMPLEX"
+    "-D_LIBCPP___FWD_COMPLEX_H"
+  ];
+
   nativeBuildInputs = [
     autoreconfHook
     gengetopt