diff --git a/src/tools/miri/src/eval.rs b/src/tools/miri/src/eval.rs
index 4734d488d049..b211f3c5f713 100644
--- a/src/tools/miri/src/eval.rs
+++ b/src/tools/miri/src/eval.rs
@@ -132,7 +132,7 @@ pub struct MiriConfig {
     pub external_so_file: Option<PathBuf>,
     /// Run a garbage collector for SbTags every N basic blocks.
     pub gc_interval: u32,
-    /// FIXME: add docs.
+    /// The number of CPUs to be reported by miri.
     pub num_cpus: u32,
 }
 
diff --git a/src/tools/miri/src/machine.rs b/src/tools/miri/src/machine.rs
index bd51207bbb19..805657ac1822 100644
--- a/src/tools/miri/src/machine.rs
+++ b/src/tools/miri/src/machine.rs
@@ -406,7 +406,7 @@ pub struct MiriMachine<'mir, 'tcx> {
     pub(crate) gc_interval: u32,
     /// The number of blocks that passed since the last SbTag GC pass.
     pub(crate) since_gc: u32,
-    /// FIXME: docs,
+    /// The number of CPUs to be reported by miri.
     pub(crate) num_cpus: u32,
 }