diff --git a/retropikzel/assert.scm b/retropikzel/assert.scm
index 4417b87..450679b 100644
--- a/retropikzel/assert.scm
+++ b/retropikzel/assert.scm
@@ -1,15 +1,4 @@
 (define-syntax assert
   (syntax-rules ()
-    ((_ check body)
-     (let ((result body))
-       (when (not (check result))
-         (error "assertion error: " check body result))
-       result))))
-
-(define-syntax asserts
-  (syntax-rules ()
-    ((_ (check ...) body)
-     (let ((result body))
-       (when (not (check result)) (error "assertion error: " check body result)) ...
-       result))))
-
+    ((_ check val err-msg)
+     (unless (check val) (error err-msg val)))))
diff --git a/retropikzel/assert.sld b/retropikzel/assert.sld
index ccd498f..68db746 100644
--- a/retropikzel/assert.sld
+++ b/retropikzel/assert.sld
@@ -1,7 +1,10 @@
+;; SPDX-License-Identifier: LGPL
+;; VERSION: 0.1.0
+;; DESCRIPTION: Assert
+;; ADDITIONAL_LIBRARIES: retropikzel/assert/pass.sld
+
 (define-library
   (retropikzel assert)
-  (import (scheme base)
-          (scheme write))
-  (export assert
-          asserts)
+  (import (scheme base))
+  (export assert)
   (include "assert.scm"))
diff --git a/retropikzel/assert/LICENSE b/retropikzel/assert/LICENSE
new file mode 100644
index 0000000..6989ebe
--- /dev/null
+++ b/retropikzel/assert/LICENSE
@@ -0,0 +1 @@
+LGPL
diff --git a/retropikzel/assert/pass.scm b/retropikzel/assert/pass.scm
new file mode 100644
index 0000000..1ef8905
--- /dev/null
+++ b/retropikzel/assert/pass.scm
@@ -0,0 +1 @@
+(define-syntax assert (syntax-rules () ((_ check val err-msg) #t)))
diff --git a/retropikzel/assert/pass.sld b/retropikzel/assert/pass.sld
new file mode 100644
index 0000000..4b52f69
--- /dev/null
+++ b/retropikzel/assert/pass.sld
@@ -0,0 +1,9 @@
+;; SPDX-License-Identifier: LGPL
+;; VERSION: 0.1.0
+;; DESCRIPTION: Assert passtrough
+
+(define-library
+  (retropikzel assert pass)
+  (import (scheme base))
+  (export assert)
+  (include "pass.scm"))
diff --git a/retropikzel/assert/test.scm b/retropikzel/assert/test.scm
index 2b8ee0e..f70fcd1 100644
--- a/retropikzel/assert/test.scm
+++ b/retropikzel/assert/test.scm
@@ -10,12 +10,17 @@
 
 (test-begin "assert")
 
-(test-equal 1 (assert number? 1))
+(define (plus a b)
+  (assert integer? a "a must be integer")
+  (assert integer? b "b must be integer")
+  (+ a b))
+
+(write (plus 5 5))
+(newline)
+(test-equal 10 (plus 5 5))
 
 (test-equal 'error
             (guard (condition (else 'error))
-              (assert number? "string")))
-
-(test-equal 1 (asserts (number? (lambda (i) (= i 1))) 1))
+              (plus 5 'a)))
 
 (test-end "assert")