diff --git a/src/boot/boot.janet b/src/boot/boot.janet
index 461e8928..0dced169 100644
--- a/src/boot/boot.janet
+++ b/src/boot/boot.janet
@@ -154,11 +154,6 @@
        ,v
        (,error ,(if err err (string/format "assert failure in %j" x))))))
 
-(defmacro assertf
-  "Convenience macro that combines `assert` and `string/format`."
-  [x & args]
-  ~(as-macro ,assert ,x (,string/format ,;args)))
-
 (defmacro defdyn
   ``Define an alias for a keyword that is used as a dynamic binding. The
   alias is a normal, lexically scoped binding that can be used instead of
@@ -210,14 +205,14 @@
   (error (string/format fmt ;args)))
 
 (defmacro assertf
-  "Throw an error if x is not truthy. Will not evaluate `err` if x is truthy."
+  "Convenience macro that combines `assert` and `string/format`."
   [x fmt & args]
   (def v (gensym))
   ~(do
      (def ,v ,x)
      (if ,v
        ,v
-       (,error (,string/format ,fmt ,;args)))))
+       (,errorf ,fmt ,;args))))
 
 (defmacro default
   ``Define a default value for an optional argument.
diff --git a/test/suite-boot.janet b/test/suite-boot.janet
index 2168c410..a598d827 100644
--- a/test/suite-boot.janet
+++ b/test/suite-boot.janet
@@ -998,11 +998,10 @@
 (setdyn *debug* nil)
 
 # issue #1516
-(assert (assertf true) "assertf 1 argument")
+(assert-error "assertf 1 argument" (macex '(assertf true)))
 (assert (assertf true "fun message") "assertf 2 arguments")
 (assert (assertf true "%s message" "mystery") "assertf 3 arguments")
 (assert (assertf (not nil) "%s message" "ordinary") "assertf not nil")
-(assert-error "assertf error 1" (assertf false))
 (assert-error "assertf error 2" (assertf false "fun message"))
 (assert-error "assertf error 3" (assertf false "%s message" "mystery"))
 (assert-error "assertf error 4" (assertf nil "%s %s" "alice" "bob"))