diff --git a/src/core/Instant.pm b/src/core/Instant.pm
index 4026e5f46af..a33f128c5c1 100644
--- a/src/core/Instant.pm
+++ b/src/core/Instant.pm
@@ -1,6 +1,6 @@
 use v6;
 
-class Instant {
+class Instant does Real {
     has Rat $.x;
       # A linear count of seconds since 1970-01-01T00:00:00Z, plus
       # tai-utc::initial-offset. Thus, $.x matches TAI from 1970