diff --git a/lib/outcome.fz b/lib/outcome.fz
index 1630d7462e..02583ab79e 100644
--- a/lib/outcome.fz
+++ b/lib/outcome.fz
@@ -65,9 +65,9 @@ is
   #
   public err error
     pre
-      safety: (outcome.this!!)
+      safety: outcome.this!!
   =>
-    outcome.this ? T       => panic "outcome.err called on successful outcome"
+    outcome.this ? T       => panic "outcome.err called on successful outcome. Enable `safety` to obtain a precondition failure for debugging."
                  | e error => e
 
 
diff --git a/lib/switch.fz b/lib/switch.fz
index ebd22129ed..725aa2e560 100644
--- a/lib/switch.fz
+++ b/lib/switch.fz
@@ -71,7 +71,7 @@ is
     safety: switch.this??
   =>
     switch.this ? a A => a
-                | B   => fuzion.std.panic "switch.get called on B"
+                | B   => fuzion.std.panic "switch.get called on B. Enable `safety` to obtain a precondition failure for debugging."
 
 
   # unwrap value or get default
@@ -91,7 +91,7 @@ is
       safety: switch.this??
   =>
     switch.this ? a A => a
-                | B   => panic "switch.val called on B"
+                | B   => panic "switch.val called on B. Enable `safety` to obtain a precondition failure for debugging."
 
 
   # value of a switch or default if switch contains B