diff --git a/pkgs/servers/http/nginx/generic.nix b/pkgs/servers/http/nginx/generic.nix
index fa7864886dc..12b873df6a4 100644
--- a/pkgs/servers/http/nginx/generic.nix
+++ b/pkgs/servers/http/nginx/generic.nix
@@ -1,5 +1,5 @@
 { stdenv, fetchurl, fetchpatch, openssl, zlib, pcre, libxml2, libxslt
-, gd, geoip
+, substituteAll, gd, geoip
 , withDebug ? false
 , withStream ? true
 , withMail ? false
@@ -75,9 +75,12 @@ stdenv.mkDerivation {
 
   preConfigure = (concatMapStringsSep "\n" (mod: mod.preConfigure or "") modules);
 
-  patches = [
-    ./nix-etag-1.15.4.patch
-  ] ++ stdenv.lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+  patches = stdenv.lib.singleton (substituteAll {
+    src = ./nix-etag-1.15.4.patch;
+    preInstall = ''
+      export nixStoreDir="$NIX_STORE" nixStoreDirLen="''${#NIX_STORE}"
+    '';
+  }) ++ stdenv.lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
     (fetchpatch {
       url = "https://raw.githubusercontent.com/openwrt/packages/master/net/nginx/patches/102-sizeof_test_fix.patch";
       sha256 = "0i2k30ac8d7inj9l6bl0684kjglam2f68z8lf3xggcc2i5wzhh8a";
diff --git a/pkgs/servers/http/nginx/nix-etag-1.15.4.patch b/pkgs/servers/http/nginx/nix-etag-1.15.4.patch
index 1a8dcb4303a..9dec715bf6c 100644
--- a/pkgs/servers/http/nginx/nix-etag-1.15.4.patch
+++ b/pkgs/servers/http/nginx/nix-etag-1.15.4.patch
@@ -36,8 +36,8 @@ index c57ec00c..b7992de2 100644
 -                                  r->headers_out.last_modified_time,
 -                                  r->headers_out.content_length_n)
 -                      - etag->value.data;
-+    #define NIX_STORE_DIR "/nix/store"
-+    #define NIX_STORE_LEN ngx_strlen(NIX_STORE_DIR)
++    #define NIX_STORE_DIR "@nixStoreDir@"
++    #define NIX_STORE_LEN @nixStoreDirLen@
 +
 +    if (r->headers_out.last_modified_time == 1
 +        && !ngx_strncmp(real, NIX_STORE_DIR, NIX_STORE_LEN)