diff --git a/book/src/exit-codes.md b/book/src/exit-codes.md
index 70253924..5b255111 100644
--- a/book/src/exit-codes.md
+++ b/book/src/exit-codes.md
@@ -11,7 +11,7 @@ cargo-mutants returns an exit code that can be used by scripts or CI.
 * **3**: Some tests timed out: possibly the mutations caused an infinite loop,
   or the timeout is too low.
 
-* **4**: The tests are already failing or hanging before any mutations are
+* **4**: The baseline tests are already failing or hanging before any mutations are
   applied, so no mutations were tested.
 
 For more detailed machine-readable information, use the [`mutants.out` directory](mutants-out.md).
diff --git a/src/exit_code.rs b/src/exit_code.rs
index 592dcab5..886182a3 100644
--- a/src/exit_code.rs
+++ b/src/exit_code.rs
@@ -24,7 +24,7 @@ pub const FOUND_PROBLEMS: i32 = 2;
 pub const TIMEOUT: i32 = 3;
 
 /// The tests are already failing in an unmutated tree.
-pub const CLEAN_TESTS_FAILED: i32 = 4;
+pub const BASELINE_FAILED: i32 = 4;
 
 /// An internal software error, from sysexit.
 pub const SOFTWARE: i32 = 70;
diff --git a/src/outcome.rs b/src/outcome.rs
index 90e6c22c..2d83ab44 100644
--- a/src/outcome.rs
+++ b/src/outcome.rs
@@ -99,7 +99,7 @@ impl LabOutcome {
             .iter()
             .any(|o| !o.scenario.is_mutant() && !o.success())
         {
-            exit_code::CLEAN_TESTS_FAILED
+            exit_code::BASELINE_FAILED
         } else if self.timeout > 0 {
             exit_code::TIMEOUT
         } else if self.missed > 0 {