diff --git a/vm/src/obj/objbytearray.rs b/vm/src/obj/objbytearray.rs
index 47300e3b0..29194142a 100644
--- a/vm/src/obj/objbytearray.rs
+++ b/vm/src/obj/objbytearray.rs
@@ -2,8 +2,6 @@
 use std::cell::{Cell, RefCell};
 use std::convert::TryFrom;
 
-use num_traits::ToPrimitive;
-
 use super::objbyteinner::{
     ByteInnerExpandtabsOptions, ByteInnerFindOptions, ByteInnerNewOptions, ByteInnerPaddingOptions,
     ByteInnerPosition, ByteInnerSplitOptions, ByteInnerSplitlinesOptions,
@@ -506,18 +504,13 @@ impl PyByteArrayRef {
     }
 
     #[pymethod(name = "insert")]
-    fn insert(self, index: PyIntRef, x: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
+    fn insert(self, mut index: isize, x: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
         let bytes = &mut self.inner.borrow_mut().elements;
         let len = isize::try_from(bytes.len())
             .map_err(|_e| vm.new_overflow_error("bytearray too big".to_string()))?;
 
         let x = x.as_bigint().byte_or(vm)?;
 
-        let mut index = index
-            .as_bigint()
-            .to_isize()
-            .ok_or_else(|| vm.new_overflow_error("index too big".to_string()))?;
-
         if index >= len {
             bytes.push(x);
             return Ok(());
@@ -550,17 +543,17 @@ impl PyByteArrayRef {
     }
 
     #[pymethod(name = "__mul__")]
-    fn repeat(self, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    fn repeat(self, n: isize, vm: &VirtualMachine) -> PyResult {
         Ok(vm.ctx.new_bytearray(self.inner.borrow().repeat(n, vm)?))
     }
 
     #[pymethod(name = "__rmul__")]
-    fn rmul(self, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    fn rmul(self, n: isize, vm: &VirtualMachine) -> PyResult {
         self.repeat(n, vm)
     }
 
     #[pymethod(name = "__imul__")]
-    fn irepeat(self, n: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
+    fn irepeat(self, n: isize, vm: &VirtualMachine) -> PyResult<()> {
         self.inner.borrow_mut().irepeat(n, vm)
     }
 
diff --git a/vm/src/obj/objbyteinner.rs b/vm/src/obj/objbyteinner.rs
index 30d21db99..5b6ca53af 100644
--- a/vm/src/obj/objbyteinner.rs
+++ b/vm/src/obj/objbyteinner.rs
@@ -1073,16 +1073,12 @@ impl PyByteInner {
         res
     }
 
-    pub fn repeat(&self, n: PyIntRef, vm: &VirtualMachine) -> PyResult<Vec<u8>> {
+    pub fn repeat(&self, n: isize, _vm: &VirtualMachine) -> PyResult<Vec<u8>> {
         if self.elements.is_empty() {
             // We can multiple an empty vector by any integer, even if it doesn't fit in an isize.
             return Ok(vec![]);
         }
 
-        let n = n.as_bigint().to_isize().ok_or_else(|| {
-            vm.new_overflow_error("can't multiply bytes that many times".to_string())
-        })?;
-
         if n <= 0 {
             Ok(vec![])
         } else {
@@ -1097,16 +1093,12 @@ impl PyByteInner {
         }
     }
 
-    pub fn irepeat(&mut self, n: PyIntRef, vm: &VirtualMachine) -> PyResult<()> {
+    pub fn irepeat(&mut self, n: isize, _vm: &VirtualMachine) -> PyResult<()> {
         if self.elements.is_empty() {
             // We can multiple an empty vector by any integer, even if it doesn't fit in an isize.
             return Ok(());
         }
 
-        let n = n.as_bigint().to_isize().ok_or_else(|| {
-            vm.new_overflow_error("can't multiply bytes that many times".to_string())
-        })?;
-
         if n <= 0 {
             self.elements.clear();
         } else {
diff --git a/vm/src/obj/objbytes.rs b/vm/src/obj/objbytes.rs
index 2aa532c87..41b329d75 100644
--- a/vm/src/obj/objbytes.rs
+++ b/vm/src/obj/objbytes.rs
@@ -421,12 +421,12 @@ impl PyBytesRef {
     }
 
     #[pymethod(name = "__mul__")]
-    fn repeat(self, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    fn repeat(self, n: isize, vm: &VirtualMachine) -> PyResult {
         Ok(vm.ctx.new_bytes(self.inner.repeat(n, vm)?))
     }
 
     #[pymethod(name = "__rmul__")]
-    fn rmul(self, n: PyIntRef, vm: &VirtualMachine) -> PyResult {
+    fn rmul(self, n: isize, vm: &VirtualMachine) -> PyResult {
         self.repeat(n, vm)
     }
 
diff --git a/vm/src/obj/objstr.rs b/vm/src/obj/objstr.rs
index 7b06adadf..0eded6e76 100644
--- a/vm/src/obj/objstr.rs
+++ b/vm/src/obj/objstr.rs
@@ -292,14 +292,10 @@ impl PyString {
     }
 
     #[pymethod(name = "__mul__")]
-    fn mul(&self, val: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
-        if !objtype::isinstance(&val, &vm.ctx.int_type()) {
-            return Err(vm.new_type_error(format!("Cannot multiply {} and {}", self, val)));
-        }
-        objint::get_value(&val)
-            .to_isize()
-            .map(|multiplier| multiplier.max(0))
-            .and_then(|multiplier| multiplier.to_usize())
+    fn mul(&self, multiplier: isize, vm: &VirtualMachine) -> PyResult<String> {
+        multiplier
+            .max(0)
+            .to_usize()
             .map(|multiplier| self.value.repeat(multiplier))
             .ok_or_else(|| {
                 vm.new_overflow_error("cannot fit 'int' into an index-sized integer".to_string())
@@ -307,7 +303,7 @@ impl PyString {
     }
 
     #[pymethod(name = "__rmul__")]
-    fn rmul(&self, val: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
+    fn rmul(&self, val: isize, vm: &VirtualMachine) -> PyResult<String> {
         self.mul(val, vm)
     }
 
@@ -1358,7 +1354,9 @@ fn try_update_quantity_from_tuple(
                         Ok(tuple_index)
                     }
                 }
-                None => Err(vm.new_type_error("not enough arguments for format string".to_string())),
+                None => {
+                    Err(vm.new_type_error("not enough arguments for format string".to_string()))
+                }
             }
         }
         _ => Ok(tuple_index),