diff --git a/vm/src/obj/objcode.rs b/vm/src/obj/objcode.rs
index 757e1aca3..f8cdcb22a 100644
--- a/vm/src/obj/objcode.rs
+++ b/vm/src/obj/objcode.rs
@@ -27,7 +27,7 @@ pub fn copy_code(code_obj: &PyObjectRef) -> bytecode::CodeObject {
 
 fn code_new(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(_cls, None)]);
-    Err(vm.new_type_error(format!("Cannot directly create code object")))
+    Err(vm.new_type_error("Cannot directly create code object".to_string()))
 }
 
 fn code_repr(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
@@ -43,7 +43,7 @@ fn code_repr(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
     };
 
     // TODO: fetch proper line info from code object
-    let line = format!(", line 1");
+    let line = ", line 1".to_string();
 
     let repr = format!("<code object at .. {}{}>", file, line);
     Ok(vm.new_str(repr))
diff --git a/vm/src/obj/objframe.rs b/vm/src/obj/objframe.rs
index c9aa366b1..e0e0d8d15 100644
--- a/vm/src/obj/objframe.rs
+++ b/vm/src/obj/objframe.rs
@@ -19,12 +19,12 @@ pub fn init(context: &PyContext) {
 
 fn frame_new(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(_cls, None)]);
-    Err(vm.new_type_error(format!("Cannot directly create frame object")))
+    Err(vm.new_type_error("Cannot directly create frame object".to_string()))
 }
 
 fn frame_repr(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
     arg_check!(vm, args, required = [(_frame, Some(vm.ctx.frame_type()))]);
-    let repr = format!("<frame object at .. >");
+    let repr = "<frame object at .. >".to_string();
     Ok(vm.new_str(repr))
 }
 
diff --git a/vm/src/obj/objsuper.rs b/vm/src/obj/objsuper.rs
index 850f64c1a..4929042bb 100644
--- a/vm/src/obj/objsuper.rs
+++ b/vm/src/obj/objsuper.rs
@@ -53,9 +53,9 @@ fn super_init(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
 
     // Check obj type:
     if !(objtype::isinstance(&py_obj, &py_type) || objtype::issubclass(&py_obj, &py_type)) {
-        return Err(vm.new_type_error(format!(
-            "super(type, obj): obj must be an instance or subtype of type"
-        )));
+        return Err(vm.new_type_error(
+            "super(type, obj): obj must be an instance or subtype of type".to_string(),
+        ));
     }
 
     // TODO: how to store those types?
diff --git a/vm/src/pyobject.rs b/vm/src/pyobject.rs
index 69fc083a5..b91b519c9 100644
--- a/vm/src/pyobject.rs
+++ b/vm/src/pyobject.rs
@@ -1037,13 +1037,13 @@ impl PyObject {
                 dict: ref _dict,
                 mro: _,
             } => format!("<class '{}'>", name),
-            PyObjectPayload::Instance { dict: _ } => format!("<instance>"),
-            PyObjectPayload::Code { code: _ } => format!("<code>"),
-            PyObjectPayload::Function { .. } => format!("<func>"),
-            PyObjectPayload::Generator { .. } => format!("<generator>"),
-            PyObjectPayload::Frame { .. } => format!("<frame>"),
-            PyObjectPayload::BoundMethod { .. } => format!("<bound-method>"),
-            PyObjectPayload::RustFunction { function: _ } => format!("<rustfunc>"),
+            PyObjectPayload::Instance { dict: _ } => "<instance>".to_string(),
+            PyObjectPayload::Code { code: _ } => "<code>".to_string(),
+            PyObjectPayload::Function { .. } => "<func>".to_string(),
+            PyObjectPayload::Generator { .. } => "<generator>".to_string(),
+            PyObjectPayload::Frame { .. } => "<frame>".to_string(),
+            PyObjectPayload::BoundMethod { .. } => "<bound-method>".to_string(),
+            PyObjectPayload::RustFunction { function: _ } => "<rustfunc>".to_string(),
             PyObjectPayload::Module { ref name, dict: _ } => format!("<module '{}'>", name),
             PyObjectPayload::Scope { ref scope } => format!("<scope '{:?}'>", scope),
             PyObjectPayload::Slice {
diff --git a/vm/src/stdlib/pystruct.rs b/vm/src/stdlib/pystruct.rs
index fda1854f4..4640af759 100644
--- a/vm/src/stdlib/pystruct.rs
+++ b/vm/src/stdlib/pystruct.rs
@@ -76,7 +76,7 @@ fn pack_bool(
         data.write_u8(v).unwrap();
         Ok(())
     } else {
-        Err(vm.new_type_error(format!("Expected boolean")))
+        Err(vm.new_type_error("Expected boolean".to_string()))
     }
 }
 
@@ -150,7 +150,7 @@ fn pack_f32(
         data.write_f32::<LittleEndian>(v).unwrap();
         Ok(())
     } else {
-        Err(vm.new_type_error(format!("Expected float")))
+        Err(vm.new_type_error("Expected float".to_string()))
     }
 }
 
@@ -164,7 +164,7 @@ fn pack_f64(
         data.write_f64::<LittleEndian>(v).unwrap();
         Ok(())
     } else {
-        Err(vm.new_type_error(format!("Expected float")))
+        Err(vm.new_type_error("Expected float".to_string()))
     }
 }
 
@@ -216,7 +216,7 @@ fn struct_pack(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
                 )))
             }
         } else {
-            Err(vm.new_type_error(format!("First argument must be of str type")))
+            Err(vm.new_type_error("First argument must be of str type".to_string()))
         }
     }
 }