diff --git a/src/libslic3r/Config.hpp b/src/libslic3r/Config.hpp
index b34b6af932..24bbe7a5b1 100644
--- a/src/libslic3r/Config.hpp
+++ b/src/libslic3r/Config.hpp
@@ -389,6 +389,8 @@ public:
         if (rhs.type() != this->type())
             throw ConfigurationError("ConfigOptionSingle: Comparing incompatible types");
         assert(dynamic_cast<const ConfigOptionSingle*>(&rhs));
+        if (this->is_nil() && rhs.is_nil())
+            return true;
         return this->value == static_cast<const ConfigOptionSingle*>(&rhs)->value;
     }
 
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index e3a184639f..dcb5a52491 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -2640,6 +2640,8 @@ std::vector<size_t> Plater::priv::load_files(const std::vector<fs::path>& input_
                         config.apply(loaded_printer_technology == ptFFF ?
                             static_cast<const ConfigBase&>(FullPrintConfig::defaults()) :
                             static_cast<const ConfigBase&>(SLAFullPrintConfig::defaults()));
+                        // Set all the nullable values in defaults to nils.
+                        config.null_nullables();
                         // and place the loaded config over the base.
                         config += std::move(config_loaded);
                     }