diff --git a/config/src/keyassignment.rs b/config/src/keyassignment.rs
index efd36fd89..0609de145 100644
--- a/config/src/keyassignment.rs
+++ b/config/src/keyassignment.rs
@@ -279,7 +279,7 @@ pub enum PaneDirection {
 impl PaneDirection {
     pub fn direction_from_str(arg: &str) -> Result<PaneDirection, String> {
         for candidate in PaneDirection::variants() {
-            if candidate.to_lowercase() == arg.to_lowercase() {
+            if candidate.eq_ignore_ascii_case(arg) {
                 if let Ok(direction) = PaneDirection::from_dynamic(
                     &Value::String(candidate.to_string()),
                     FromDynamicOptions::default(),
diff --git a/config/src/version.rs b/config/src/version.rs
index b3a3ebdf9..d009f1e13 100644
--- a/config/src/version.rs
+++ b/config/src/version.rs
@@ -32,7 +32,7 @@ pub fn running_under_wsl() -> bool {
                 std::ffi::CStr::from_ptr(name.version.as_ptr()).to_string_lossy(),
                 std::ffi::CStr::from_ptr(name.release.as_ptr()).to_string_lossy()
             );
-            return version.to_lowercase().contains("microsoft");
+            return version.to_ascii_lowercase().contains("microsoft");
         }
     };
 
diff --git a/wezterm-font/src/parser.rs b/wezterm-font/src/parser.rs
index d229530e1..8206853ec 100644
--- a/wezterm-font/src/parser.rs
+++ b/wezterm-font/src/parser.rs
@@ -432,7 +432,7 @@ impl ParsedFont {
         // fontconfig resorts to name matching, so we do too :-/
         let style = match style {
             FontStyle::Normal => {
-                let lower = names.full_name.to_lowercase();
+                let lower = names.full_name.to_ascii_lowercase();
                 if lower.contains("italic") || lower.contains("kursiv") {
                     FontStyle::Italic
                 } else if lower.contains("oblique") {
@@ -442,7 +442,7 @@ impl ParsedFont {
                 }
             }
             FontStyle::Italic => {
-                let lower = names.full_name.to_lowercase();
+                let lower = names.full_name.to_ascii_lowercase();
                 if lower.contains("oblique") {
                     FontStyle::Oblique
                 } else {
@@ -802,7 +802,7 @@ impl ParsedFont {
                 // This heuristic is awful, TBH.
                 if !self.is_built_in_fallback
                     && !attr.is_synthetic
-                    && self.names.full_name.to_lowercase().contains("moji")
+                    && self.names.full_name.to_ascii_lowercase().contains("moji")
                 {
                     self.assume_emoji_presentation = true;
                 }
diff --git a/wezterm-gui/src/main.rs b/wezterm-gui/src/main.rs
index a669a1e7d..234c7eebb 100644
--- a/wezterm-gui/src/main.rs
+++ b/wezterm-gui/src/main.rs
@@ -139,7 +139,7 @@ async fn async_run_ssh(opts: SshCommand) -> anyhow::Result<()> {
         ssh_option.insert("wezterm_ssh_verbose".to_string(), "true".to_string());
     }
     for (k, v) in opts.config_override {
-        ssh_option.insert(k.to_lowercase().to_string(), v);
+        ssh_option.insert(k.to_ascii_lowercase(), v);
     }
 
     let dom = SshDomain {
diff --git a/wezterm-ssh/src/config.rs b/wezterm-ssh/src/config.rs
index d1e19bc92..78b9470f5 100644
--- a/wezterm-ssh/src/config.rs
+++ b/wezterm-ssh/src/config.rs
@@ -296,7 +296,7 @@ impl ParsedConfigFile {
                     let mut tokens = v.split_ascii_whitespace();
 
                     while let Some(cname) = tokens.next() {
-                        match cname.to_lowercase().as_str() {
+                        match cname.to_ascii_lowercase().as_str() {
                             "all" => {
                                 criteria.push(Criteria::All);
                             }