diff --git a/2018/inputs/01 b/2018/inputs/01.txt
similarity index 100%
rename from 2018/inputs/01
rename to 2018/inputs/01.txt
diff --git a/2018/inputs/02 b/2018/inputs/02.txt
similarity index 100%
rename from 2018/inputs/02
rename to 2018/inputs/02.txt
diff --git a/2018/inputs/03 b/2018/inputs/03.txt
similarity index 100%
rename from 2018/inputs/03
rename to 2018/inputs/03.txt
diff --git a/2018/inputs/04 b/2018/inputs/04.txt
similarity index 100%
rename from 2018/inputs/04
rename to 2018/inputs/04.txt
diff --git a/2018/inputs/05 b/2018/inputs/05.txt
similarity index 100%
rename from 2018/inputs/05
rename to 2018/inputs/05.txt
diff --git a/2018/inputs/06 b/2018/inputs/06.txt
similarity index 100%
rename from 2018/inputs/06
rename to 2018/inputs/06.txt
diff --git a/2018/src/day03.rs b/2018/src/day03.rs
index b86b800..a9f224f 100644
--- a/2018/src/day03.rs
+++ b/2018/src/day03.rs
@@ -103,7 +103,7 @@ mod tests {
 
     use super::*;
 
-    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/03");
+    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/03.txt");
 
     #[test]
     fn sample_part1() {
diff --git a/2018/src/day04.rs b/2018/src/day04.rs
index 95877bc..a9a3249 100644
--- a/2018/src/day04.rs
+++ b/2018/src/day04.rs
@@ -119,7 +119,7 @@ mod tests {
     use common::Solution;
     use day04::Day04;
 
-    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/04");
+    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/04.txt");
 
     #[test]
     fn sample_part1() {
diff --git a/2018/src/day05.rs b/2018/src/day05.rs
index 3644cbe..9f14516 100644
--- a/2018/src/day05.rs
+++ b/2018/src/day05.rs
@@ -55,7 +55,7 @@ mod tests {
     use common::Solution;
     use day05::Day05;
 
-    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/05");
+    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/05.txt");
 
     #[test]
     fn sample_part1() {
diff --git a/2018/src/day06.rs b/2018/src/day06.rs
index c35244c..e5640ee 100644
--- a/2018/src/day06.rs
+++ b/2018/src/day06.rs
@@ -145,7 +145,7 @@ mod tests {
     use common::Solution;
     use day06::Day06;
 
-    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/06");
+    const SAMPLE_INPUT: &[u8] = include_bytes!("samples/06.txt");
 
     #[test]
     fn sample_part1() {
diff --git a/2018/src/samples/03 b/2018/src/samples/03.txt
similarity index 100%
rename from 2018/src/samples/03
rename to 2018/src/samples/03.txt
diff --git a/2018/src/samples/04 b/2018/src/samples/04.txt
similarity index 100%
rename from 2018/src/samples/04
rename to 2018/src/samples/04.txt
diff --git a/2018/src/samples/05 b/2018/src/samples/05.txt
similarity index 100%
rename from 2018/src/samples/05
rename to 2018/src/samples/05.txt
diff --git a/2018/src/samples/06 b/2018/src/samples/06.txt
similarity index 100%
rename from 2018/src/samples/06
rename to 2018/src/samples/06.txt