diff --git a/src/intrinsic.rs b/src/intrinsic.rs
index b7338d4d5214..b62838fbc8bb 100644
--- a/src/intrinsic.rs
+++ b/src/intrinsic.rs
@@ -134,7 +134,7 @@ fn call_intrinsic(
                     "xsub" => mir::BinOp::Sub,
                     _ => bug!(),
                 };
-                // FIXME: what do atomics do on overflow?
+                // Atomics wrap around on overflow.
                 self.binop_ignore_overflow(op, old, rhs, ptr.into())?;
             }