diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
--- a/Lib/test/test_complex.py
+++ b/Lib/test/test_complex.py
@@ -304,6 +304,7 @@
         self.assertRaises(TypeError, float, 5+3j)
         self.assertRaises(ValueError, complex, "")
         self.assertRaises(TypeError, complex, None)
+        self.assertRaisesRegex(TypeError, "not 'NoneType'", complex, None)
         self.assertRaises(ValueError, complex, "\0")
         self.assertRaises(ValueError, complex, "3\09")
         self.assertRaises(TypeError, complex, "1", "2")
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
--- a/Lib/test/test_float.py
+++ b/Lib/test/test_float.py
@@ -41,6 +41,7 @@
         self.assertRaises(ValueError, float, "-.")
         self.assertRaises(ValueError, float, b"-")
         self.assertRaises(TypeError, float, {})
+        self.assertRaisesRegex(TypeError, "not 'dict'", float, {})
         # Lone surrogate
         self.assertRaises(UnicodeEncodeError, float, '\uD8F0')
         # check that we don't accept alternate exponent markers
diff --git a/Objects/complexobject.c b/Objects/complexobject.c
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -773,8 +773,9 @@
             goto error;
     }
     else if (PyObject_AsCharBuffer(v, &s, &len)) {
-        PyErr_SetString(PyExc_TypeError,
-                        "complex() argument must be a string or a number");
+        PyErr_Format(PyExc_TypeError,
+            "complex() argument must be a string or a number, not '%.200s'",
+            Py_TYPE(v)->tp_name);
         return NULL;
     }
 
@@ -953,8 +954,9 @@
         nbi = i->ob_type->tp_as_number;
     if (nbr == NULL || nbr->nb_float == NULL ||
         ((i != NULL) && (nbi == NULL || nbi->nb_float == NULL))) {
-        PyErr_SetString(PyExc_TypeError,
-                   "complex() argument must be a string or a number");
+        PyErr_Format(PyExc_TypeError,
+            "complex() argument must be a string or a number, not '%.200s'",
+            Py_TYPE(r)->tp_name);
         if (own_r) {
             Py_DECREF(r);
         }
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -149,8 +149,9 @@
         }
     }
     else if (PyObject_AsCharBuffer(v, &s, &len)) {
-        PyErr_SetString(PyExc_TypeError,
-            "float() argument must be a string or a number");
+        PyErr_Format(PyExc_TypeError,
+            "float() argument must be a string or a number, not '%.200s'",
+            Py_TYPE(v)->tp_name);
         return NULL;
     }
     last = s + len;