diff --git a/.github/.cspell/project-dictionary.txt b/.github/.cspell/project-dictionary.txt
index 3644ae06..c4b5c08f 100644
--- a/.github/.cspell/project-dictionary.txt
+++ b/.github/.cspell/project-dictionary.txt
@@ -8,6 +8,7 @@ fcoverage
 fprofile
 instrprof
 libhello
+mcdc
 microkernel
 MSYSTEM
 nextest
diff --git a/src/main.rs b/src/main.rs
index 44475e76..9ccf5201 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1013,6 +1013,16 @@ impl Format {
                     "-show-line-counts-or-regions",
                     "-show-expansions",
                     "-show-branches=count",
+                ]);
+                if cmd!(&cx.llvm_cov, "show", "--help")
+                    .read()
+                    .unwrap_or_default()
+                    .contains("-show-mcdc")
+                {
+                    // -show-mcdc requires LLVM 18+
+                    cmd.arg("-show-mcdc");
+                }
+                cmd.args([
                     &format!("-Xdemangler={}", cx.current_exe.display()),
                     "-Xdemangler=llvm-cov",
                     "-Xdemangler=demangle",