diff --git a/pkgs/development/interpreters/spidermonkey/38.nix b/pkgs/development/interpreters/spidermonkey/38.nix
index d48cf841b048..2c45ba589767 100644
--- a/pkgs/development/interpreters/spidermonkey/38.nix
+++ b/pkgs/development/interpreters/spidermonkey/38.nix
@@ -1,6 +1,8 @@
-{ stdenv, fetchurl, pkgconfig, gnused_422, perl, python2, zip, libffi, readline, icu, zlib, nspr
+{ stdenv, fetchurl, pkgconfig, gnused_422, perl, python2, zip, libffi, readline, icu, zlib, buildPackages
 , libobjc }:
 
+with stdenv.lib;
+
 stdenv.mkDerivation rec {
   version = "38.8.0";
   name = "spidermonkey-${version}";
@@ -10,7 +12,7 @@ stdenv.mkDerivation rec {
     sha256 = "10lrync6cxnjlnadc0j3vg8r2dq9b3wwanw8qj1h6ncxwb7asxcl";
   };
 
-  buildInputs = [ libffi readline icu zlib nspr ]
+  buildInputs = [ libffi readline icu zlib ]
                ++ stdenv.lib.optional stdenv.isDarwin libobjc;
   nativeBuildInputs = [ pkgconfig perl python2 zip gnused_422 ];
 
@@ -19,13 +21,13 @@ stdenv.mkDerivation rec {
   preConfigure = ''
     export CXXFLAGS="-fpermissive"
     export LIBXUL_DIST=$out
-    export PYTHON="${python2.interpreter}"
+    export PYTHON="${buildPackages.python2.interpreter}"
   '';
 
   configureFlags = [
     "--enable-threadsafe"
     "--with-system-ffi"
-    "--with-system-nspr"
+    "--enable-posix-nspr-emulation"
     "--with-system-zlib"
     "--with-system-icu"
     "--enable-readline"
@@ -34,8 +36,17 @@ stdenv.mkDerivation rec {
     # not be good defaults for other uses.
     "--enable-gcgenerational"
     "--enable-shared-js"
+  ] ++ optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    # Spidermonkey seems to use different host/build terminology for cross
+    # compilation here.
+    "--host=${stdenv.buildPlatform.config}"
+    "--target=${stdenv.hostPlatform.config}"
   ];
 
+  configurePlatforms = [];
+
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
+
   # This addresses some build system bug. It's quite likely to be safe
   # to re-enable parallel builds if the source revision changes.
   enableParallelBuilding = true;
diff --git a/pkgs/development/interpreters/spidermonkey/60.nix b/pkgs/development/interpreters/spidermonkey/60.nix
index 1dfaf9a22860..518fc5f77b72 100644
--- a/pkgs/development/interpreters/spidermonkey/60.nix
+++ b/pkgs/development/interpreters/spidermonkey/60.nix
@@ -1,6 +1,8 @@
-{ stdenv, fetchurl, fetchpatch, autoconf213, pkgconfig, perl, python2, zip
+{ stdenv, fetchurl, fetchpatch, autoconf213, pkgconfig, perl, python2, zip, buildPackages
 , which, readline, zlib, icu }:
 
+with stdenv.lib;
+
 let
   version = "60.4.0";
 in stdenv.mkDerivation rec {
@@ -24,7 +26,7 @@ in stdenv.mkDerivation rec {
   preConfigure = ''
     export CXXFLAGS="-fpermissive"
     export LIBXUL_DIST=$out
-    export PYTHON="${python2.interpreter}"
+    export PYTHON="${buildPackages.python2.interpreter}"
 
     # We can't build in js/src/, so create a build dir
     mkdir obj
@@ -45,8 +47,17 @@ in stdenv.mkDerivation rec {
     # https://src.fedoraproject.org/rpms/mozjs38/c/761399aba092bcb1299bb4fccfd60f370ab4216e
     "--enable-optimize"
     "--enable-release"
+  ] ++ optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    # Spidermonkey seems to use different host/build terminology for cross
+    # compilation here.
+    "--host=${stdenv.buildPlatform.config}"
+    "--target=${stdenv.hostPlatform.config}"
   ];
 
+  configurePlatforms = [];
+
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
+
   # Remove unnecessary static lib
   preFixup = ''
     rm $out/lib/libjs_static.ajs