diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index ff7722c739..1d2a203c2e 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -2407,6 +2407,7 @@ def = this->add("filament_loading_speed", coFloats);
     def->label = L("Filter out tiny gaps");
     def->category = L("Layers and Perimeters");
     def->tooltip = L("Filter out gaps smaller than the threshold specified");
+    def->sidetext = L("mm");
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(0));