diff --git a/libtiledbsoma/src/utils/nanoarrow.c b/libtiledbsoma/src/utils/nanoarrow.c
index c946c01362..156f6c87e2 100644
--- a/libtiledbsoma/src/utils/nanoarrow.c
+++ b/libtiledbsoma/src/utils/nanoarrow.c
@@ -1713,6 +1713,10 @@ int64_t ArrowSchemaToString(const struct ArrowSchema* schema, char* out, int64_t
     return snprintf(out, n, "[invalid: schema is released]");
   }
 
+  if (out == NULL) {
+    return snprintf(out, n, "[invalid: out is released]");
+  }
+
   struct ArrowSchemaView schema_view;
   struct ArrowError error;