diff --git a/basis/combinators/short-circuit/smart/smart.factor b/basis/combinators/short-circuit/smart/smart.factor
index 141077ea3a..ca659cacbe 100644
--- a/basis/combinators/short-circuit/smart/smart.factor
+++ b/basis/combinators/short-circuit/smart/smart.factor
@@ -1,11 +1,18 @@
 
-USING: kernel sequences math stack-checker accessors macros
+USING: kernel sequences math stack-checker effects accessors macros
        combinators.short-circuit ;
 
 IN: combinators.short-circuit.smart
 
-MACRO: && ( quots -- quot )
-  dup first infer [ in>> ] [ out>> ] bi - 1+ n&&-rewrite ;
+<PRIVATE
 
-MACRO: || ( quots -- quot )
-  dup first infer [ in>> ] [ out>> ] bi - 1+ n||-rewrite ;
+: arity ( quots -- n )
+    first infer
+    dup terminated?>> [ "Cannot determine arity" throw ] when
+    effect-height neg 1+ ;
+
+PRIVATE>
+
+MACRO: && ( quots -- quot ) dup arity n&&-rewrite ;
+
+MACRO: || ( quots -- quot ) dup arity n||-rewrite ;