diff --git a/pkgs/picotls/default.nix b/pkgs/picotls/default.nix
index 8a1657c..09c8cb3 100644
--- a/pkgs/picotls/default.nix
+++ b/pkgs/picotls/default.nix
@@ -6,6 +6,14 @@
 , fetchFromGitHub
 }:
 
+let
+  picotest = fetchFromGitHub {
+    owner = "h2o";
+    repo = "picotest";
+    rev = "6906d90b39684b8b2c18db5b0c7412128140655d";
+    sha256 = "1z26mcg40bkrgbxgh4469y97lixls00p75k9j9dw1w18bg8mg49n";
+  };
+in
 stdenv.mkDerivation rec {
   pname = "picotls";
   version = "20201012";
@@ -14,7 +22,7 @@ stdenv.mkDerivation rec {
     owner = "h2o";
     repo = "picotls";
     rev = "9238121fa7788e8642072b6d4d1a2f2fb71db242";
-    sha256 = "01hl9s2jxh792kfzhc12ha9x1wwk9g869k6n4m83cccdnkmghg8j";
+    sha256 = "0yam62yd606q8v515r74l110gmch4i4bif9hfxn7mgvcdv979l7d";
   };
 
   outputs = [ "out" "dev" ];
@@ -29,6 +37,14 @@ stdenv.mkDerivation rec {
     openssl
   ];
 
+  patchPhase = ''
+    sed -i 's|deps/picotest|${picotest}|g' CMakeLists.txt
+    sed -i 's|../deps/picotest|${picotest}|g' t/picotls.c
+    sed -i 's|../deps/picotest|${picotest}|g' t/minicrypto.c
+    sed -i 's|../deps/picotest|${picotest}|g' t/openssl.c
+    sed -i 's|../deps/picotest|${picotest}|g' t/fusion.c
+  '';
+
   installPhase = ''
     runHook preInstall