diff --git a/py/obj.c b/py/obj.c
index 5a05ea58c5..b461fe50aa 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -383,22 +383,7 @@ mp_float_t mp_obj_get_float(mp_obj_t arg) {
 
 #if MICROPY_PY_BUILTINS_COMPLEX
 bool mp_obj_get_complex_maybe(mp_obj_t arg, mp_float_t *real, mp_float_t *imag) {
-    if (arg == mp_const_false) {
-        *real = 0;
-        *imag = 0;
-    } else if (arg == mp_const_true) {
-        *real = 1;
-        *imag = 0;
-    } else if (mp_obj_is_small_int(arg)) {
-        *real = (mp_float_t)MP_OBJ_SMALL_INT_VALUE(arg);
-        *imag = 0;
-    #if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
-    } else if (mp_obj_is_exact_type(arg, &mp_type_int)) {
-        *real = mp_obj_int_as_float_impl(arg);
-        *imag = 0;
-    #endif
-    } else if (mp_obj_is_float(arg)) {
-        *real = mp_obj_float_get(arg);
+    if (mp_obj_get_float_maybe(arg, real)) {
         *imag = 0;
     } else if (mp_obj_is_type(arg, &mp_type_complex)) {
         mp_obj_complex_get(arg, real, imag);
diff --git a/py/objcomplex.c b/py/objcomplex.c
index 3c4cb66140..4aa598a0bc 100644
--- a/py/objcomplex.c
+++ b/py/objcomplex.c
@@ -89,11 +89,8 @@ STATIC mp_obj_t complex_make_new(const mp_obj_type_t *type_in, size_t n_args, si
                 return args[0];
             } else {
                 mp_float_t real, imag;
-                if (mp_obj_get_complex_maybe(args[0], &real, &imag)) {
-                    return mp_obj_new_complex(real, imag);
-                }
-                // something else, try to cast it to a complex
-                return mp_obj_new_complex(mp_obj_get_float(args[0]), 0);
+                mp_obj_get_complex(args[0], &real, &imag);
+                return mp_obj_new_complex(real, imag);
             }
 
         case 2:
diff --git a/tests/float/cmath_dunder.py b/tests/float/cmath_dunder.py
new file mode 100644
index 0000000000..3526341510
--- /dev/null
+++ b/tests/float/cmath_dunder.py
@@ -0,0 +1,21 @@
+# test that cmath functions support user classes with __float__ and __complex__
+
+try:
+    import cmath
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+
+class TestFloat:
+    def __float__(self):
+        return 1.0
+
+
+class TestComplex:
+    def __complex__(self):
+        return 1j + 10
+
+
+for clas in TestFloat, TestComplex:
+    print("%.5g" % cmath.phase(clas()))
diff --git a/tests/float/complex_dunder.py b/tests/float/complex_dunder.py
index 128dc69293..975d829b47 100644
--- a/tests/float/complex_dunder.py
+++ b/tests/float/complex_dunder.py
@@ -1,6 +1,11 @@
 # test __complex__ function support
 
 
+class TestFloat:
+    def __float__(self):
+        return 1.0
+
+
 class TestComplex:
     def __complex__(self):
         return 1j + 10
@@ -20,6 +25,7 @@ class Test:
     pass
 
 
+print(complex(TestFloat()))
 print(complex(TestComplex()))
 
 try:
diff --git a/tests/float/math_dunder.py b/tests/float/math_dunder.py
new file mode 100644
index 0000000000..33ea7f7c1c
--- /dev/null
+++ b/tests/float/math_dunder.py
@@ -0,0 +1,15 @@
+# test that math functions support user classes with __float__
+
+try:
+    import math
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+
+class TestFloat:
+    def __float__(self):
+        return 1.0
+
+
+print("%.5g" % math.exp(TestFloat()))