diff --git a/pkgs/by-name/sc/screen/package.nix b/pkgs/by-name/sc/screen/package.nix
index 308c4ef1921f2..0dc36a39d3b6a 100644
--- a/pkgs/by-name/sc/screen/package.nix
+++ b/pkgs/by-name/sc/screen/package.nix
@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
   ];
 
   # We need _GNU_SOURCE so that mallocmock_reset() is defined: https://savannah.gnu.org/bugs/?66416
-  NIX_CFLAGS_COMPILE = "-D_GNU_SOURCE=1 -Wno-int-conversion -Wno-incompatible-pointer-types";
+  env.NIX_CFLAGS_COMPILE = "-D_GNU_SOURCE=1 -Wno-int-conversion -Wno-incompatible-pointer-types";
 
   nativeBuildInputs = [
     autoreconfHook
diff --git a/pkgs/development/interpreters/python/pypy/default.nix b/pkgs/development/interpreters/python/pypy/default.nix
index 7779b3fbba8fa..fa97386d68ced 100644
--- a/pkgs/development/interpreters/python/pypy/default.nix
+++ b/pkgs/development/interpreters/python/pypy/default.nix
@@ -120,14 +120,16 @@ stdenv.mkDerivation rec {
   dontPatchShebangs = true;
   disallowedReferences = [ python ];
 
-  # fix compiler error in curses cffi module, where char* != const char*
-  NIX_CFLAGS_COMPILE =
-    if stdenv.cc.isClang then "-Wno-error=incompatible-function-pointer-types" else null;
-  C_INCLUDE_PATH = lib.makeSearchPathOutput "dev" "include" buildInputs;
-  LIBRARY_PATH = lib.makeLibraryPath buildInputs;
-  LD_LIBRARY_PATH = lib.makeLibraryPath (
-    builtins.filter (x: x.outPath != stdenv.cc.libc.outPath or "") buildInputs
-  );
+  env = {
+    # fix compiler error in curses cffi module, where char* != const char*
+    NIX_CFLAGS_COMPILE =
+      if stdenv.cc.isClang then "-Wno-error=incompatible-function-pointer-types" else null;
+    C_INCLUDE_PATH = lib.makeSearchPathOutput "dev" "include" buildInputs;
+    LIBRARY_PATH = lib.makeLibraryPath buildInputs;
+    LD_LIBRARY_PATH = lib.makeLibraryPath (
+      builtins.filter (x: x.outPath != stdenv.cc.libc.outPath or "") buildInputs
+    );
+  };
 
   patches = [
     ./dont_fetch_vendored_deps.patch