diff --git a/vm/src/builtins/dict.rs b/vm/src/builtins/dict.rs
index 35ab231d4..c98b9fd3c 100644
--- a/vm/src/builtins/dict.rs
+++ b/vm/src/builtins/dict.rs
@@ -355,10 +355,7 @@ impl PyDict {
     ) -> PyResult {
         match self.entries.pop(vm, &key)? {
             Some(value) => Ok(value),
-            None => match default {
-                OptionalArg::Present(default) => Ok(default),
-                OptionalArg::Missing => Err(vm.new_key_error(key)),
-            },
+            None => default.ok_or_else(|| vm.new_key_error(key)),
         }
     }
 
diff --git a/vm/src/builtins/enumerate.rs b/vm/src/builtins/enumerate.rs
index 106bb30df..302a25082 100644
--- a/vm/src/builtins/enumerate.rs
+++ b/vm/src/builtins/enumerate.rs
@@ -41,11 +41,9 @@ impl SlotConstructor for PyEnumerate {
     type Args = EnumerateArgs;
 
     fn py_new(cls: PyTypeRef, args: Self::Args, vm: &VirtualMachine) -> PyResult {
-        let counter = match args.start {
-            OptionalArg::Present(start) => start.as_bigint().clone(),
-            OptionalArg::Missing => BigInt::zero(),
-        };
-
+        let counter = args
+            .start
+            .map_or_else(BigInt::zero, |start| start.as_bigint().clone());
         let iterator = iterator::get_iter(vm, args.iterable)?;
         PyEnumerate {
             counter: PyRwLock::new(counter),
diff --git a/vm/src/builtins/make_module.rs b/vm/src/builtins/make_module.rs
index 1058dd428..4a812518a 100644
--- a/vm/src/builtins/make_module.rs
+++ b/vm/src/builtins/make_module.rs
@@ -519,10 +519,7 @@ mod decl {
     ) -> PyResult {
         iterator::call_next(vm, &iterator).or_else(|err| {
             if err.isinstance(&vm.ctx.exceptions.stop_iteration) {
-                match default_value {
-                    OptionalArg::Missing => Err(err),
-                    OptionalArg::Present(value) => Ok(value),
-                }
+                default_value.ok_or(err)
             } else {
                 Err(err)
             }
diff --git a/vm/src/builtins/pybool.rs b/vm/src/builtins/pybool.rs
index cc1b31187..5d7f07bdb 100644
--- a/vm/src/builtins/pybool.rs
+++ b/vm/src/builtins/pybool.rs
@@ -105,10 +105,7 @@ impl SlotConstructor for PyBool {
                 actual_type
             )));
         }
-        let val = match x {
-            OptionalArg::Present(val) => boolval(vm, val)?,
-            OptionalArg::Missing => false,
-        };
+        let val = x.map_or(Ok(false), |val| boolval(vm, val))?;
         Ok(vm.ctx.new_bool(val))
     }
 }
diff --git a/vm/src/builtins/pystr.rs b/vm/src/builtins/pystr.rs
index 5b376500b..2845fe4f0 100644
--- a/vm/src/builtins/pystr.rs
+++ b/vm/src/builtins/pystr.rs
@@ -909,14 +909,13 @@ impl PyStr {
         pad: fn(&str, usize, char, usize) -> String,
         vm: &VirtualMachine,
     ) -> PyResult<String> {
-        let fillchar = match fillchar {
-            OptionalArg::Present(ref s) => s.value.chars().exactly_one().map_err(|_| {
+        let fillchar = fillchar.map_or(Ok(' '), |ref s| {
+            s.value.chars().exactly_one().map_err(|_| {
                 vm.new_type_error(
                     "The fill character must be exactly one character long".to_owned(),
                 )
-            }),
-            OptionalArg::Missing => Ok(' '),
-        }?;
+            })
+        })?;
         Ok(if self.len() as isize >= width {
             String::from(self.as_str())
         } else {
diff --git a/vm/src/stdlib/math.rs b/vm/src/stdlib/math.rs
index 1b062ca16..36cb40a04 100644
--- a/vm/src/stdlib/math.rs
+++ b/vm/src/stdlib/math.rs
@@ -69,15 +69,8 @@ struct IsCloseArgs {
 fn math_isclose(args: IsCloseArgs, vm: &VirtualMachine) -> PyResult<bool> {
     let a = args.a.to_f64();
     let b = args.b.to_f64();
-    let rel_tol = match args.rel_tol {
-        OptionalArg::Missing => 1e-09,
-        OptionalArg::Present(ref value) => value.to_f64(),
-    };
-
-    let abs_tol = match args.abs_tol {
-        OptionalArg::Missing => 0.0,
-        OptionalArg::Present(ref value) => value.to_f64(),
-    };
+    let rel_tol = args.rel_tol.map_or(1e-09, |value| value.to_f64());
+    let abs_tol = args.abs_tol.map_or(0.0, |value| value.to_f64());
 
     if rel_tol < 0.0 || abs_tol < 0.0 {
         return Err(vm.new_value_error("tolerances must be non-negative".to_owned()));
diff --git a/vm/src/stdlib/sre.rs b/vm/src/stdlib/sre.rs
index 31d930838..382d7ce36 100644
--- a/vm/src/stdlib/sre.rs
+++ b/vm/src/stdlib/sre.rs
@@ -654,12 +654,10 @@ mod _sre {
             group: OptionalArg<PyObjectRef>,
             vm: &VirtualMachine,
         ) -> PyResult<(isize, isize)> {
-            let index = match group {
-                OptionalArg::Present(group) => self
-                    .get_index(group, vm)
-                    .ok_or_else(|| vm.new_index_error("no such group".to_owned()))?,
-                OptionalArg::Missing => 0,
-            };
+            let index = group.map_or(Ok(0), |group| {
+                self.get_index(group, vm)
+                    .ok_or_else(|| vm.new_index_error("no such group".to_owned()))
+            })?;
             Ok(self.regs[index])
         }