diff --git a/src/args/matches.rs b/src/args/matches.rs
index e728f99..641c6fc 100644
--- a/src/args/matches.rs
+++ b/src/args/matches.rs
@@ -158,7 +158,7 @@ mod tests {
 	fn test_matches() {
 		let args = Args::default();
 		let matches = ArgMatches::new(&args);
-		let key = format!("{}_general_test", env!("CARGO_PKG_NAME")).to_uppercase();
+		let key = concat!(env!("CARGO_PKG_NAME"), "_general_test").to_uppercase();
 		env::set_var(&key, "...");
 		assert_eq!("...", matches.get_env("test").unwrap_or_default());
 		assert_eq!(Some("..."), matches.value_of("test"));
diff --git a/src/file/mod.rs b/src/file/mod.rs
index ca1f036..3ae9975 100644
--- a/src/file/mod.rs
+++ b/src/file/mod.rs
@@ -8,9 +8,6 @@ use std::ffi::OsStr;
 use std::fs;
 use std::path::{Path, PathBuf};
 
-/* Extension of the configuration file */
-const CONFIG_FILE_EXTENSION: &str = "conf";
-
 /* Representation of the output file */
 #[derive(Debug)]
 pub struct File {
@@ -85,13 +82,12 @@ impl File {
 	 */
 	pub fn get_config_file() -> Option<PathBuf> {
 		if let Ok(config_file) =
-			env::var(format!("{}_CONFIG", env!("CARGO_PKG_NAME")).to_uppercase())
+			env::var(concat!(env!("CARGO_PKG_NAME"), "_CONFIG").to_uppercase())
 		{
 			return Some(PathBuf::from(config_file));
 		}
 		if let Some(config_dir) = dirs::config_dir() {
-			let file_name =
-				format!("{}.{}", env!("CARGO_PKG_NAME"), CONFIG_FILE_EXTENSION);
+			let file_name = concat!(env!("CARGO_PKG_NAME"), ".conf");
 			for config_file in [
 				config_dir.join(&file_name),
 				config_dir.join(env!("CARGO_PKG_NAME")).join(&file_name),
diff --git a/src/settings.rs b/src/settings.rs
index 01be680..5e27c78 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -201,7 +201,7 @@ mod tests {
 		let matches = ArgMatches::new(&args);
 		let mut settings = AppSettings::new(&matches);
 		env::set_var(
-			format!("{}_general_color", env!("CARGO_PKG_NAME")).to_uppercase(),
+			concat!(env!("CARGO_PKG_NAME"), "_general_color").to_uppercase(),
 			"d473d4",
 		);
 		assert_eq!(
diff --git a/src/util/logger.rs b/src/util/logger.rs
index a57cb88..78ff03a 100644
--- a/src/util/logger.rs
+++ b/src/util/logger.rs
@@ -78,7 +78,7 @@ impl<'a> Logger<'a> {
 			.level(self.level_filter);
 		if self.settings.save.file.format.is_animation() {
 			logger = logger.level_for(
-				format!("{}::edit", env!("CARGO_PKG_NAME")),
+				concat!(env!("CARGO_PKG_NAME"), "::edit"),
 				LevelFilter::Warn,
 			)
 		}
@@ -95,7 +95,7 @@ mod tests {
 	#[test]
 	fn test_logger() -> Result<(), SetLoggerError> {
 		let quiet_var =
-			format!("{}_GENERAL_QUIET", env!("CARGO_PKG_NAME").to_uppercase());
+			concat!(env!("CARGO_PKG_NAME"), "_GENERAL_QUIET").to_uppercase();
 		env::set_var(quiet_var, "true");
 		let args = Args::default();
 		let matches = ArgMatches::new(&args);
diff --git a/src/x11/mod.rs b/src/x11/mod.rs
index df0fca5..49447f9 100644
--- a/src/x11/mod.rs
+++ b/src/x11/mod.rs
@@ -87,7 +87,8 @@ unsafe extern "C" fn handle_x11_errors(
 		{
 			CStr::from_ptr(error_text.as_mut_ptr() as *mut c_char)
 				.to_string_lossy()
-				.into_owned() + " "
+				.into_owned()
+				+ " "
 		} else {
 			String::from("Unknown error ")
 		},