diff --git a/extra/math/primes/primes.factor b/extra/math/primes/primes.factor
index 2db81982d8..d93910ec02 100644
--- a/extra/math/primes/primes.factor
+++ b/extra/math/primes/primes.factor
@@ -7,7 +7,7 @@ IN: math.primes
 <PRIVATE
 
 : find-prime-miller-rabin ( n -- p )
-    dup miller-rabin [ 2 + find-prime-miller-rabin ] unless ; foldable
+    [ dup miller-rabin ] [ 2 + ] [ ] until ; foldable
 
 PRIVATE>