diff --git a/pkgs/tools/networking/darkstat/default.nix b/pkgs/tools/networking/darkstat/default.nix
index 04cab365578..2da581776d2 100644
--- a/pkgs/tools/networking/darkstat/default.nix
+++ b/pkgs/tools/networking/darkstat/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, libpcap, zlib }:
+{ lib, stdenv, fetchpatch, fetchurl, libpcap, zlib }:
 
 stdenv.mkDerivation rec {
   version = "3.0.719";
@@ -9,6 +9,15 @@ stdenv.mkDerivation rec {
     sha256 = "1mzddlim6dhd7jhr4smh0n2fa511nvyjhlx76b03vx7phnar1bxf";
   };
 
+  patches = [
+    # Avoid multiple definitions of CLOCK_REALTIME on macOS 11,
+    # see https://github.com/emikulic/darkstat/pull/2
+    (fetchpatch {
+       url = "https://github.com/emikulic/darkstat/commit/d2fd232e1167dee6e7a2d88b9ab7acf2a129f697.diff";
+       sha256 = "0z5mpyc0q65qb6cn4xcrxl0vx21d8ibzaam5kjyrcw4icd8yg4jb";
+    })
+  ];
+
   buildInputs = [ libpcap zlib ];
 
   enableParallelBuilding = true;