diff --git a/extra/math/extras/extras.factor b/extra/math/extras/extras.factor
index b907f25583..b78e06464a 100644
--- a/extra/math/extras/extras.factor
+++ b/extra/math/extras/extras.factor
@@ -152,6 +152,11 @@ PRIVATE>
 : nan-max ( seq -- n )
     [ fp-nan? not ] filter supremum ;
 
+: fill-nans ( seq -- newseq )
+    [ first ] keep [
+        dup fp-nan? [ drop dup ] [ nip dup ] if
+    ] map nip ;
+
 : sinc ( x -- y )
     [ 1 ] [ pi * [ sin ] [ / ] bi ] if-zero ;