diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 5089ac7b..b1899562 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -109,7 +109,7 @@ jobs:
       - name: Install Rust toolchain
         uses: artichoke/setup-rust/build-and-test@v1.9.0
         with:
-          toolchain: "1.56.0"
+          toolchain: "1.58.0"
 
       - name: Compile
         run: cargo build --verbose
diff --git a/Cargo.toml b/Cargo.toml
index 437d342f..cdfc90f0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ version = "1.8.0" # remember to set `html_root_url` in `src/lib.rs`.
 authors = ["Ryan Lopopolo <rjl@hyperbo.la>"]
 license = "MIT"
 edition = "2021"
-rust-version = "1.56.0"
+rust-version = "1.58.0"
 readme = "README.md"
 repository = "https://github.com/artichoke/intaglio"
 documentation = "https://docs.rs/intaglio"
diff --git a/README.md b/README.md
index d4aeba49..38522766 100644
--- a/README.md
+++ b/README.md
@@ -136,7 +136,7 @@ All features are enabled by default.
 
 ### Minimum Supported Rust Version
 
-This crate requires at least Rust 1.56.0. This version can be bumped in minor
+This crate requires at least Rust 1.58.0. This version can be bumped in minor
 releases.
 
 ## License
diff --git a/src/internal.rs b/src/internal.rs
index ea114cf0..6ab0041e 100644
--- a/src/internal.rs
+++ b/src/internal.rs
@@ -353,3 +353,201 @@ impl fmt::Debug for Slice<Path> {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use core::fmt::Write;
+    use std::borrow::Cow;
+    #[cfg(feature = "cstr")]
+    use std::ffi::CStr;
+    #[cfg(feature = "osstr")]
+    use std::ffi::OsStr;
+    #[cfg(feature = "path")]
+    use std::path::Path;
+
+    use super::Interned;
+
+    #[test]
+    fn test_interned_static_str_debug_format() {
+        let s = Interned::from(Cow::Borrowed("abc"));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+
+    #[test]
+    fn test_interned_owned_str_debug_format() {
+        let s = Interned::<str>::from(Cow::Owned("abc".to_string()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+
+    #[test]
+    #[cfg(feature = "bytes")]
+    fn test_interned_static_bytes_debug_format() {
+        let s = Interned::from(Cow::Borrowed(&b"abc"[..]));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "[97, 98, 99]");
+
+        let s = Interned::from(Cow::Borrowed(&b"\xFF"[..]));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "[255]");
+
+        let s = Interned::from(Cow::Borrowed(&b"abc"[..]));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::from(Cow::Borrowed(&b"\xFF"[..]));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"\u{FFFD}\"");
+    }
+
+    #[test]
+    #[cfg(feature = "bytes")]
+    fn test_interned_owned_bytes_debug_format() {
+        let s = Interned::<[u8]>::from(Cow::Owned(b"abc".to_vec()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "[97, 98, 99]");
+
+        let s = Interned::<[u8]>::from(Cow::Owned(b"\xFF".to_vec()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "[255]");
+
+        let s = Interned::<[u8]>::from(Cow::Owned(b"abc".to_vec()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::<[u8]>::from(Cow::Owned(b"\xFF".to_vec()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"\u{FFFD}\"");
+    }
+
+    #[test]
+    #[cfg(feature = "cstr")]
+    fn test_interned_static_cstr_debug_format() {
+        let s = Interned::from(Cow::Borrowed(
+            CStr::from_bytes_with_nul(b"abc\x00").unwrap(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::from(Cow::Borrowed(
+            CStr::from_bytes_with_nul(b"\xFF\x00").unwrap(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, r#""\xff""#);
+
+        let s = Interned::from(Cow::Borrowed(
+            CStr::from_bytes_with_nul(b"abc\x00").unwrap(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::from(Cow::Borrowed(
+            CStr::from_bytes_with_nul(b"\xFF\x00").unwrap(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"\u{FFFD}\"");
+    }
+
+    #[test]
+    #[cfg(feature = "cstr")]
+    fn test_interned_owned_cstring_debug_format() {
+        let s = Interned::<CStr>::from(Cow::Owned(
+            CStr::from_bytes_with_nul(b"abc\x00").unwrap().to_owned(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::<CStr>::from(Cow::Owned(
+            CStr::from_bytes_with_nul(b"\xFF\x00").unwrap().to_owned(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, r#""\xff""#);
+
+        let s = Interned::<CStr>::from(Cow::Owned(
+            CStr::from_bytes_with_nul(b"abc\x00").unwrap().to_owned(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::<CStr>::from(Cow::Owned(
+            CStr::from_bytes_with_nul(b"\xFF\x00").unwrap().to_owned(),
+        ));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"\u{FFFD}\"");
+    }
+
+    #[test]
+    #[cfg(feature = "osstr")]
+    fn test_interned_static_osstr_debug_format() {
+        let s = Interned::from(Cow::Borrowed(OsStr::new("abc")));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::from(Cow::Borrowed(OsStr::new("abc")));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+
+    #[test]
+    #[cfg(feature = "osstr")]
+    fn test_interned_owned_osstring_debug_format() {
+        let s = Interned::<OsStr>::from(Cow::Owned(OsStr::new("abc").to_owned()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::<OsStr>::from(Cow::Owned(OsStr::new("abc").to_owned()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+
+    #[test]
+    #[cfg(feature = "path")]
+    fn test_interned_static_path_debug_format() {
+        let s = Interned::from(Cow::Borrowed(Path::new("abc")));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::from(Cow::Borrowed(Path::new("abc")));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+
+    #[test]
+    #[cfg(feature = "path")]
+    fn test_interned_owned_pathbuf_debug_format() {
+        let s = Interned::<Path>::from(Cow::Owned(Path::new("abc").to_owned()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+
+        let s = Interned::<Path>::from(Cow::Owned(Path::new("abc").to_owned()));
+        let mut buf = String::new();
+        write!(&mut buf, "{s:#?}").unwrap();
+        assert_eq!(buf, "\"abc\"");
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 1f5a25ce..e002a973 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -296,7 +296,7 @@ mod tests {
     fn error_display_is_not_empty() {
         let tc = SymbolOverflowError::new();
         let mut buf = String::new();
-        write!(&mut buf, "{}", tc).unwrap();
+        write!(&mut buf, "{tc}").unwrap();
         assert!(!buf.is_empty());
     }
 
@@ -304,7 +304,7 @@ mod tests {
     fn error_debug_is_not_empty() {
         let tc = SymbolOverflowError::new();
         let mut buf = String::new();
-        write!(&mut buf, "{:?}", tc).unwrap();
+        write!(&mut buf, "{tc:?}").unwrap();
         assert!(!buf.is_empty());
     }