diff --git a/src/libslic3r/Format/3mf.cpp b/src/libslic3r/Format/3mf.cpp
index eb4822634..0be336181 100644
--- a/src/libslic3r/Format/3mf.cpp
+++ b/src/libslic3r/Format/3mf.cpp
@@ -56,59 +56,59 @@ const std::string SLA_SUPPORT_POINTS_FILE = "Metadata/Slic3r_PE_sla_support_poin
 const std::string SLA_DRAIN_HOLES_FILE = "Metadata/Slic3r_PE_sla_drain_holes.txt";
 const std::string CUSTOM_GCODE_PER_PRINT_Z_FILE = "Metadata/Prusa_Slicer_custom_gcode_per_print_z.xml";
 
-static constexpr char* MODEL_TAG = "model";
-static constexpr char* RESOURCES_TAG = "resources";
-static constexpr char* OBJECT_TAG = "object";
-static constexpr char* MESH_TAG = "mesh";
-static constexpr char* VERTICES_TAG = "vertices";
-static constexpr char* VERTEX_TAG = "vertex";
-static constexpr char* TRIANGLES_TAG = "triangles";
-static constexpr char* TRIANGLE_TAG = "triangle";
-static constexpr char* COMPONENTS_TAG = "components";
-static constexpr char* COMPONENT_TAG = "component";
-static constexpr char* BUILD_TAG = "build";
-static constexpr char* ITEM_TAG = "item";
-static constexpr char* METADATA_TAG = "metadata";
+static constexpr const char* MODEL_TAG = "model";
+static constexpr const char* RESOURCES_TAG = "resources";
+static constexpr const char* OBJECT_TAG = "object";
+static constexpr const char* MESH_TAG = "mesh";
+static constexpr const char* VERTICES_TAG = "vertices";
+static constexpr const char* VERTEX_TAG = "vertex";
+static constexpr const char* TRIANGLES_TAG = "triangles";
+static constexpr const char* TRIANGLE_TAG = "triangle";
+static constexpr const char* COMPONENTS_TAG = "components";
+static constexpr const char* COMPONENT_TAG = "component";
+static constexpr const char* BUILD_TAG = "build";
+static constexpr const char* ITEM_TAG = "item";
+static constexpr const char* METADATA_TAG = "metadata";
 
-static constexpr char* CONFIG_TAG = "config";
-static constexpr char* VOLUME_TAG = "volume";
+static constexpr const char* CONFIG_TAG = "config";
+static constexpr const char* VOLUME_TAG = "volume";
 
-static constexpr char* UNIT_ATTR = "unit";
-static constexpr char* NAME_ATTR = "name";
-static constexpr char* TYPE_ATTR = "type";
-static constexpr char* ID_ATTR = "id";
-static constexpr char* X_ATTR = "x";
-static constexpr char* Y_ATTR = "y";
-static constexpr char* Z_ATTR = "z";
-static constexpr char* V1_ATTR = "v1";
-static constexpr char* V2_ATTR = "v2";
-static constexpr char* V3_ATTR = "v3";
-static constexpr char* OBJECTID_ATTR = "objectid";
-static constexpr char* TRANSFORM_ATTR = "transform";
-static constexpr char* PRINTABLE_ATTR = "printable";
-static constexpr char* INSTANCESCOUNT_ATTR = "instances_count";
-static constexpr char* CUSTOM_SUPPORTS_ATTR = "slic3rpe:custom_supports";
-static constexpr char* CUSTOM_SEAM_ATTR = "slic3rpe:custom_seam";
+static constexpr const char* UNIT_ATTR = "unit";
+static constexpr const char* NAME_ATTR = "name";
+static constexpr const char* TYPE_ATTR = "type";
+static constexpr const char* ID_ATTR = "id";
+static constexpr const char* X_ATTR = "x";
+static constexpr const char* Y_ATTR = "y";
+static constexpr const char* Z_ATTR = "z";
+static constexpr const char* V1_ATTR = "v1";
+static constexpr const char* V2_ATTR = "v2";
+static constexpr const char* V3_ATTR = "v3";
+static constexpr const char* OBJECTID_ATTR = "objectid";
+static constexpr const char* TRANSFORM_ATTR = "transform";
+static constexpr const char* PRINTABLE_ATTR = "printable";
+static constexpr const char* INSTANCESCOUNT_ATTR = "instances_count";
+static constexpr const char* CUSTOM_SUPPORTS_ATTR = "slic3rpe:custom_supports";
+static constexpr const char* CUSTOM_SEAM_ATTR = "slic3rpe:custom_seam";
 
-static constexpr char* KEY_ATTR = "key";
-static constexpr char* VALUE_ATTR = "value";
-static constexpr char* FIRST_TRIANGLE_ID_ATTR = "firstid";
-static constexpr char* LAST_TRIANGLE_ID_ATTR = "lastid";
+static constexpr const char* KEY_ATTR = "key";
+static constexpr const char* VALUE_ATTR = "value";
+static constexpr const char* FIRST_TRIANGLE_ID_ATTR = "firstid";
+static constexpr const char* LAST_TRIANGLE_ID_ATTR = "lastid";
 
-static constexpr char* OBJECT_TYPE = "object";
-static constexpr char* VOLUME_TYPE = "volume";
+static constexpr const char* OBJECT_TYPE = "object";
+static constexpr const char* VOLUME_TYPE = "volume";
 
-static constexpr char* NAME_KEY = "name";
-static constexpr char* MODIFIER_KEY = "modifier";
-static constexpr char* VOLUME_TYPE_KEY = "volume_type";
-static constexpr char* MATRIX_KEY = "matrix";
-static constexpr char* SOURCE_FILE_KEY = "source_file";
-static constexpr char* SOURCE_OBJECT_ID_KEY = "source_object_id";
-static constexpr char* SOURCE_VOLUME_ID_KEY = "source_volume_id";
-static constexpr char* SOURCE_OFFSET_X_KEY = "source_offset_x";
-static constexpr char* SOURCE_OFFSET_Y_KEY = "source_offset_y";
-static constexpr char* SOURCE_OFFSET_Z_KEY = "source_offset_z";
-static constexpr char* SOURCE_IN_INCHES    = "source_in_inches";
+static constexpr const char* NAME_KEY = "name";
+static constexpr const char* MODIFIER_KEY = "modifier";
+static constexpr const char* VOLUME_TYPE_KEY = "volume_type";
+static constexpr const char* MATRIX_KEY = "matrix";
+static constexpr const char* SOURCE_FILE_KEY = "source_file";
+static constexpr const char* SOURCE_OBJECT_ID_KEY = "source_object_id";
+static constexpr const char* SOURCE_VOLUME_ID_KEY = "source_volume_id";
+static constexpr const char* SOURCE_OFFSET_X_KEY = "source_offset_x";
+static constexpr const char* SOURCE_OFFSET_Y_KEY = "source_offset_y";
+static constexpr const char* SOURCE_OFFSET_Z_KEY = "source_offset_z";
+static constexpr const char* SOURCE_IN_INCHES    = "source_in_inches";
 
 const unsigned int VALID_OBJECT_TYPES_COUNT = 1;
 const char* VALID_OBJECT_TYPES[] =