diff --git a/default.nix b/default.nix
index a6890c2..0aa028c 100644
--- a/default.nix
+++ b/default.nix
@@ -195,7 +195,7 @@ let
           postPatch = (passedAttrs.postPatch or "") + ''
             # Tell poetry not to resolve the path dependencies. Any version is
             # fine !
-            yj -tj < pyproject.toml | python ${./pyproject-without-path.py} > pyproject.json
+            yj -tj < pyproject.toml | ${python.interpreter} ${./pyproject-without-path.py} > pyproject.json
             yj -jt < pyproject.json > pyproject.toml
             rm pyproject.json
           '';
diff --git a/mk-poetry-dep.nix b/mk-poetry-dep.nix
index 9537045..095497a 100644
--- a/mk-poetry-dep.nix
+++ b/mk-poetry-dep.nix
@@ -112,7 +112,7 @@ pythonPackages.callPackage (
           builtins.map (n: pythonPackages.${lib.toLower n}) (builtins.attrNames dependencies);
 
         meta = {
-          broken = ! isCompatible python.version python-versions;
+          broken = ! isCompatible python.pythonVersion python-versions;
           license = [];
         };
 
diff --git a/overrides.nix b/overrides.nix
index 58fa251..a7e9c34 100644
--- a/overrides.nix
+++ b/overrides.nix
@@ -21,11 +21,15 @@ self: super:
     }
   );
 
-  cffi = super.cffi.overrideAttrs (
-    old: {
-      buildInputs = old.buildInputs ++ [ pkgs.libffi ];
-    }
-  );
+  cffi =
+    # cffi is bundled with pypy
+    if self.python.implementation == "pypy" then null else (
+      super.cffi.overrideAttrs (
+        old: {
+          buildInputs = old.buildInputs ++ [ pkgs.libffi ];
+        }
+      )
+    );
 
   cftime = super.cftime.overrideAttrs (
     old: {
diff --git a/pep508.nix b/pep508.nix
index 93a3953..e5825da 100644
--- a/pep508.nix
+++ b/pep508.nix
@@ -83,7 +83,10 @@ let
   # This function also performs variable substitution, replacing environment markers with their explicit values
   transformExpressions = exprs: let
     variables = {
-      os_name = "posix"; # TODO: Check other platforms
+      os_name = (
+        if python.pname == "jython" then "java"
+        else "posix"
+      );
       sys_platform = (
         if stdenv.isLinux then "linux"
         else if stdenv.isDarwin then "darwin"
@@ -100,7 +103,7 @@ let
       platform_version = ""; # Field not reproducible
       python_version = python.passthru.pythonVersion;
       python_full_version = python.version;
-      implementation_name = "cpython"; # Only cpython supported for now
+      implementation_name = python.implementation;
       implementation_version = python.version;
       extra = "";
     };
diff --git a/tests/default.nix b/tests/default.nix
index 4a0602f..e6857f9 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -29,15 +29,16 @@ builtins.removeAttrs
       inherit poetry2nix poetry;
       inherit (pkgs) postgresql;
     };
+    pyqt5 = pkgs.callPackage ./pyqt5 { inherit poetry2nix; };
+    eggs = pkgs.callPackage ./eggs { inherit poetry2nix; };
 
+    # Test building poetry
     inherit poetry;
     poetry-python2 = poetry.override { python = pkgs.python2; };
 
-    # Pyqt5 test is waiting for nixpkgs sip bump to reach channel
-    pyqt5 = pkgs.callPackage ./pyqt5 { inherit poetry2nix; };
-
-    # Egg support not yet in channel, uncomment when channel progressed
-    eggs = pkgs.callPackage ./eggs { inherit poetry2nix; };
+    # And also test with pypy
+    poetry-pypy = poetry.override { python = pkgs.pypy; };
+    poetry-pypy3 = poetry.override { python = pkgs.pypy3; };
 
     inherit (poetry2nix) doc;