diff --git a/src/accountmanager.rs b/src/accountmanager.rs
index 9726454..88c37ab 100644
--- a/src/accountmanager.rs
+++ b/src/accountmanager.rs
@@ -318,6 +318,12 @@ impl Manifest {
 		self.entries.iter().any(|e| e.account_name.is_empty())
 	}
 
+	fn has_any_uppercase_in_account_names(&self) -> bool {
+		self.entries
+			.iter()
+			.any(|e| e.account_name != e.account_name.to_lowercase())
+	}
+
 	/// Performs auto-upgrades on the manifest. Returns true if any upgrades were performed.
 	pub fn auto_upgrade(&mut self) -> anyhow::Result<bool, ManifestAccountLoadError> {
 		debug!("Performing auto-upgrade...");
@@ -331,6 +337,14 @@ impl Manifest {
 			upgraded = true;
 		}
 
+		if self.has_any_uppercase_in_account_names() {
+			debug!("Lowercasing account names");
+			for i in 0..self.entries.len() {
+				self.entries[i].account_name = self.entries[i].account_name.to_lowercase();
+			}
+			upgraded = true;
+		}
+
 		Ok(upgraded)
 	}
 }
diff --git a/src/main.rs b/src/main.rs
index 68e7fb7..3056a9b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -354,7 +354,7 @@ fn do_subcmd_setup(
 ) -> anyhow::Result<()> {
 	println!("Log in to the account that you want to link to steamguard-cli");
 	print!("Username: ");
-	let username = tui::prompt();
+	let username = tui::prompt().to_lowercase();
 	let account_name = username.clone();
 	if manifest.account_exists(&username) {
 		bail!(