diff --git a/src/libslic3r/Print.cpp b/src/libslic3r/Print.cpp
index b4a2a1b3e..9dad843a9 100644
--- a/src/libslic3r/Print.cpp
+++ b/src/libslic3r/Print.cpp
@@ -2138,6 +2138,7 @@ std::string Print::output_filename(const std::string &filename_base) const
     // Set the placeholders for the data know first after the G-code export is finished.
     // These values will be just propagated into the output file name.
     DynamicConfig config = this->finished() ? this->print_statistics().config() : this->print_statistics().placeholders();
+    config.set_key_value("num_extruders", new ConfigOptionInt((int)m_config.nozzle_diameter.size()));
     return this->PrintBase::output_filename(m_config.output_filename_format.value, ".gcode", filename_base, &config);
 }