diff --git a/src/lib/core/diag.h b/src/lib/core/diag.h
index 3a817a659..276bf2362 100644
--- a/src/lib/core/diag.h
+++ b/src/lib/core/diag.h
@@ -117,12 +117,11 @@ error_unref(struct error *e)
 	while (--to_delete->refs == 0) {
 		/* Unlink error from lists completely.*/
 		struct error *cause = to_delete->cause;
-		if (to_delete->effect != NULL)
-			to_delete->effect->cause = to_delete->cause;
-		if (to_delete->cause != NULL)
-			to_delete->cause->effect = to_delete->effect;
-		to_delete->cause = NULL;
-		to_delete->effect = NULL;
+		assert(to_delete->effect == NULL);
+		if (to_delete->cause != NULL) {
+			to_delete->cause->effect = NULL;
+			to_delete->cause = NULL;
+		}
 		to_delete->destroy(to_delete);
 		if (cause == NULL)
 			return;