diff --git a/src/libslic3r/PresetBundle.hpp b/src/libslic3r/PresetBundle.hpp
index 63523ecfb1..62edbc14b2 100644
--- a/src/libslic3r/PresetBundle.hpp
+++ b/src/libslic3r/PresetBundle.hpp
@@ -161,7 +161,7 @@ public:
 
     struct VendorCache {
         static constexpr uint32_t CACHE_MAGIC   = 0x4F52435A; // "ORCZ"
-        static constexpr uint32_t CACHE_VERSION = 5; // bumped: Semver serialized as 3-part (to_string_sf)
+        static constexpr uint32_t CACHE_VERSION = 6;
 
         uint32_t    cache_version        = CACHE_VERSION;
         uint32_t    config_options_count = 0; // fixed-width: size_t varies between 32/64-bit builds
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index b51eef8aa3..d59608f467 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -2186,7 +2186,8 @@ namespace cereal {
             archive(serialization_key_ordinal);
             assert(serialization_key_ordinal > 0);
             auto it = Slic3r::print_config_def.by_serialization_key_ordinal.find(serialization_key_ordinal);
-            assert(it != Slic3r::print_config_def.by_serialization_key_ordinal.end());
+            if (it == Slic3r::print_config_def.by_serialization_key_ordinal.end())
+                throw std::runtime_error("VendorCache: unknown serialization_key_ordinal " + std::to_string(serialization_key_ordinal) + " - cache is stale");
             config.set_key_value(it->second->opt_key, it->second->load_option_from_archive(archive));
         }
     }