diff --git a/py/modmath.c b/py/modmath.c
index 0c70f34cd1..7c51eab03a 100644
--- a/py/modmath.c
+++ b/py/modmath.c
@@ -32,9 +32,8 @@
 #include <math.h>
 
 // M_PI is not part of the math.h standard and may not be defined
-#ifndef M_PI
-#define M_PI (3.14159265358979323846)
-#endif
+// And by defining our own we can ensure it uses the correct const format.
+#define MP_PI MICROPY_FLOAT_CONST(3.14159265358979323846)
 
 /// \module math - mathematical functions
 ///
@@ -204,13 +203,13 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_math_modf_obj, mp_math_modf);
 
 /// \function radians(x)
 STATIC mp_obj_t mp_math_radians(mp_obj_t x_obj) {
-    return mp_obj_new_float(mp_obj_get_float(x_obj) * M_PI / 180.0);
+    return mp_obj_new_float(mp_obj_get_float(x_obj) * (MP_PI / MICROPY_FLOAT_CONST(180.0)));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_math_radians_obj, mp_math_radians);
 
 /// \function degrees(x)
 STATIC mp_obj_t mp_math_degrees(mp_obj_t x_obj) {
-    return mp_obj_new_float(mp_obj_get_float(x_obj) * 180.0 / M_PI);
+    return mp_obj_new_float(mp_obj_get_float(x_obj) * (MICROPY_FLOAT_CONST(180.0) / MP_PI));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_math_degrees_obj, mp_math_degrees);
 
diff --git a/py/mpconfig.h b/py/mpconfig.h
index fd82b079cc..3945a1a5ab 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -505,10 +505,12 @@ typedef long long mp_longint_impl_t;
 
 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
 #define MICROPY_PY_BUILTINS_FLOAT (1)
+#define MICROPY_FLOAT_CONST(x) x##F
 #define MICROPY_FLOAT_C_FUN(fun) fun##f
 typedef float mp_float_t;
 #elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
 #define MICROPY_PY_BUILTINS_FLOAT (1)
+#define MICROPY_FLOAT_CONST(x) x
 #define MICROPY_FLOAT_C_FUN(fun) fun
 typedef double mp_float_t;
 #else
diff --git a/py/parsenum.c b/py/parsenum.c
index 1010ad3055..b1c449c9b8 100644
--- a/py/parsenum.c
+++ b/py/parsenum.c
@@ -227,7 +227,7 @@ mp_obj_t mp_parse_num_decimal(const char *str, size_t len, bool allow_imag, bool
                 } else {
                     if (in == PARSE_DEC_IN_FRAC) {
                         dec_val += dig * frac_mult;
-                        frac_mult *= 0.1;
+                        frac_mult *= MICROPY_FLOAT_CONST(0.1);
                     } else {
                         dec_val = 10 * dec_val + dig;
                     }