diff --git a/.gitignore b/.gitignore
index 099aa2e..4306ebe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
-./build
-./meliae/_intset.c
-./meliae/_loader.c
-./meliae/_scanner.c
+build/
+__pycache__/
+meliae/_intset.c
+meliae/_loader.c
+meliae/_scanner.c
 ./tags
diff --git a/meliae/_scanner_core.c b/meliae/_scanner_core.c
index 6ae7d83..8ca2923 100644
--- a/meliae/_scanner_core.c
+++ b/meliae/_scanner_core.c
@@ -98,7 +98,7 @@ _var_object_size(PyVarObject *c_obj)
         PyErr_Clear();
     }
     return _basic_object_size((PyObject *)c_obj)
-            + num_entries * c_obj->ob_type->tp_itemsize;
+            + num_entries * Py_TYPE(c_obj)->tp_itemsize;
 }
 
 static Py_ssize_t
@@ -172,10 +172,17 @@ static Py_ssize_t
 _size_of_dict(PyDictObject *c_obj)
 {
     Py_ssize_t size;
+#if PY_MAJOR_VERSION >= 3
+    PyObject* long_size;
+
+    long_size = _PyDict_SizeOf(c_obj);
+    size = PyLong_AsSize_t(long_size);
+#else
     size = _basic_object_size((PyObject *)c_obj);
     if (c_obj->ma_table != c_obj->ma_smalltable) {
         size += sizeof(PyDictEntry) * (c_obj->ma_mask + 1);
     }
+#endif
     return size;
 }
 
@@ -185,7 +192,7 @@ _size_of_unicode(PyUnicodeObject *c_obj)
 {
     Py_ssize_t size;
     size = _basic_object_size((PyObject *)c_obj);
-    size += Py_UNICODE_SIZE * c_obj->length;
+    size += Py_UNICODE_SIZE * PyUnicode_GetSize(c_obj);
     return size;
 }
 
@@ -515,7 +522,11 @@ _dump_object_to_ref_info(struct ref_info *info, PyObject *c_obj, int recurse)
     } else if (PyClass_Check(c_obj)) {
         /* Old style class */
         _write_static_to_info(info, ", \"name\": ");
+#if PY_MAJOR_VERSION >= 3
+        _dump_string(info, ((PyClassObject *)c_obj)->tp_name);
+#else
         _dump_string(info, ((PyClassObject *)c_obj)->cl_name);
+#endif
     }
     if (PyString_Check(c_obj)) {
         _write_to_ref_info(info, ", \"len\": " SSIZET_FMT, PyString_GET_SIZE(c_obj));
diff --git a/meliae/_scanner_core.h b/meliae/_scanner_core.h
index 12b5599..1910520 100644
--- a/meliae/_scanner_core.h
+++ b/meliae/_scanner_core.h
@@ -25,8 +25,14 @@
 #include <Python.h>
 #include <code.h>
 #include <frameobject.h>
+#include <dictobject.h>
 #include <stdio.h>
 
+#if PY_MAJOR_VERSION >= 3
+#define PyClassObject PyTypeObject
+#define PyClass_Check(obj) PyObject_IsInstance(obj, (PyObject *)&PyType_Type)
+#endif
+
 /**
  * Compute the size of the data directly addressed by this object.
  *
diff --git a/meliae/files.py b/meliae/files.py
index 3575031..9155815 100644
--- a/meliae/files.py
+++ b/meliae/files.py
@@ -54,7 +54,7 @@ def open_file(filename):
             process = subprocess.Popen(['gzip', '-d', '-c', filename],
                 stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE, close_fds=close_fds)
-        except OSError, e:
+        except OSError as e:
             if e.errno == errno.ENOENT:
                 # failing that, use another python process
                 return _open_mprocess(filename)
@@ -71,7 +71,7 @@ def terminate_or_pass():
                 # no longer running.
                 try:
                     return terminate()
-                except OSError, e:
+                except OSError as e:
                     sys.stderr.write('Ignoring failure to terminate process:'
                                      ' %s\n' % (e,))
                 # We *could* check if process.poll() returns that the
diff --git a/meliae/perf_counter.py b/meliae/perf_counter.py
index 51481fc..6688ee5 100644
--- a/meliae/perf_counter.py
+++ b/meliae/perf_counter.py
@@ -111,17 +111,18 @@ def get_memory(self, process):
         finally:
             f.close()
         m = re.search(r'(?i)vmpeak:\s*(?P<peak>\d+) kB', content)
-	peak = current = None
+
+        peak = current = None
         if m is not None:
-	   peak = int(m.group('peak')) * 1024
+            peak = int(m.group('peak')) * 1024
         m = re.search(r'(?i)vmsize:\s*(?P<current>\d+) kB', content)
         if m is not None:
-	   current = int(m.group('current')) * 1024
-	return current, peak
+            current = int(m.group('current')) * 1024
 
+        return current, peak
 
-class _Win32PerformanceCounter(PerformanceCounter):
 
+class _Win32PerformanceCounter(PerformanceCounter):
     def get_timer(self):
         # This returns wall-clock time, but using a much higher precision than
         # time.time() [which has a resolution of only 15ms]
diff --git a/setup.py b/setup.py
index 6375e12..7fe448a 100644
--- a/setup.py
+++ b/setup.py
@@ -12,6 +12,7 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+from __future__ import print_function
 
 
 def config():
@@ -64,7 +65,7 @@ def config():
     try:
         from Cython.Distutils import build_ext
     except ImportError:
-        print "We require Cython to be installed."
+        print("We require Cython to be installed.")
         return
 
     kwargs["cmdclass"] = {"build_ext": build_ext}