diff --git a/src/pocketpy.cpp b/src/pocketpy.cpp
index 6dbfa6bc..49c22bcd 100644
--- a/src/pocketpy.cpp
+++ b/src/pocketpy.cpp
@@ -135,11 +135,13 @@ void init_builtins(VM* _vm) {
         return VAR(MappingProxy(mod));
     });
 
-    _vm->bind(_vm->builtins, "round(x, ndigits=0)", [](VM* vm, ArgsView args) {
+    _vm->bind(_vm->builtins, "round(x, ndigits=None)", [](VM* vm, ArgsView args) {
         f64 x = CAST(f64, args[0]);
+        if(args[1] == vm->None) return x >= 0 ? VAR((i64)(x + 0.5)) : VAR((i64)(x - 0.5));
         int ndigits = CAST(int, args[1]);
         if(ndigits == 0){
-            return x >= 0 ? VAR((i64)(x + 0.5)) : VAR((i64)(x - 0.5));
+            if(is_int(args[0])) return x >= 0 ? VAR((i64)(x + 0.5)) : VAR((i64)(x - 0.5));
+            else return x >= 0 ? VAR(f64((i64)(x + 0.5))) : VAR(f64((i64)(x - 0.5)));
         }
         if(ndigits < 0) vm->ValueError("ndigits should be non-negative");
         if(x >= 0){
diff --git a/tests/70_builtins.py b/tests/70_builtins.py
index ed703c5f..212061e5 100644
--- a/tests/70_builtins.py
+++ b/tests/70_builtins.py
@@ -2,6 +2,10 @@ assert round(23.2) == 23
 assert round(23.8) == 24
 assert round(-23.2) == -23
 assert round(-23.8) == -24
+assert round(23.2, 0) == 23.0
+assert round(23.8, 0) == 24.0
+assert round(-23.2, 0) == -23.0
+assert round(-23.8, 0) == -24.0
 # round with precision
 assert round(23.2, 1) == 23.2
 assert round(23.8, 1) == 23.8