diff --git a/instant-xml-macros/Cargo.toml b/instant-xml-macros/Cargo.toml
index b37ea5a..fb59668 100644
--- a/instant-xml-macros/Cargo.toml
+++ b/instant-xml-macros/Cargo.toml
@@ -2,6 +2,7 @@
 name = "instant-xml-macros"
 version = "0.1.0"
 edition = "2021"
+rust-version = "1.58"
 workspace = ".."
 license = "Apache-2.0 OR MIT"
 
diff --git a/instant-xml-macros/src/ser.rs b/instant-xml-macros/src/ser.rs
index 7ea8e51..322717d 100644
--- a/instant-xml-macros/src/ser.rs
+++ b/instant-xml-macros/src/ser.rs
@@ -271,7 +271,7 @@ fn named_field(
                         quote!(""),
                         syn::Error::new(
                             field_meta.ns.uri.span(),
-                            &format!("unknown prefix `{prefix}` (prefix must be defined on the field's type)"),
+                            format!("unknown prefix `{prefix}` (prefix must be defined on the field's type)"),
                         )
                         .into_compile_error(),
                     ),
diff --git a/instant-xml/Cargo.toml b/instant-xml/Cargo.toml
index af1b0a6..32d6c15 100644
--- a/instant-xml/Cargo.toml
+++ b/instant-xml/Cargo.toml
@@ -2,6 +2,7 @@
 name = "instant-xml"
 version = "0.1.0"
 edition = "2021"
+rust-version = "1.58"
 workspace = ".."
 license = "Apache-2.0 OR MIT"
 
diff --git a/instant-xml/src/de.rs b/instant-xml/src/de.rs
index e313117..7d4c268 100644
--- a/instant-xml/src/de.rs
+++ b/instant-xml/src/de.rs
@@ -322,10 +322,10 @@ impl<'xml> Iterator for Context<'xml> {
                     return Some(Ok(Node::Text(text.as_str())));
                 }
                 Ok(Token::Declaration { .. }) => match self.stack.is_empty() {
-                    false => return Some(Err(Error::UnexpectedToken(format!("{:?}", token)))),
+                    false => return Some(Err(Error::UnexpectedToken(format!("{token:?}")))),
                     true => {}
                 },
-                Ok(token) => return Some(Err(Error::UnexpectedToken(format!("{:?}", token)))),
+                Ok(token) => return Some(Err(Error::UnexpectedToken(format!("{token:?}")))),
                 Err(e) => return Some(Err(Error::Parse(e))),
             }
         }
diff --git a/instant-xml/src/ser.rs b/instant-xml/src/ser.rs
index 773c8ca..b469f61 100644
--- a/instant-xml/src/ser.rs
+++ b/instant-xml/src/ser.rs
@@ -86,7 +86,7 @@ impl<'xml, W: fmt::Write + ?Sized> Serializer<'xml, W> {
             return Err(Error::UnexpectedState("invalid state for scalar"));
         }
 
-        self.output.write_fmt(format_args!("{}", value))?;
+        self.output.write_fmt(format_args!("{value}"))?;
         self.state = State::Element;
         Ok(())
     }