diff --git a/include/GCodePathConfig.h b/include/GCodePathConfig.h
index 4531b650aa..82a2ea78dd 100644
--- a/include/GCodePathConfig.h
+++ b/include/GCodePathConfig.h
@@ -18,6 +18,8 @@ namespace cura
  */
 struct GCodePathConfig
 {
+    static constexpr double FAN_SPEED_DEFAULT = -1.0;
+
     coord_t z_offset{}; //<! vertical offset from 'full' layer height
     PrintFeatureType type{}; //!< name of the feature type
     coord_t line_width{}; //!< width of the line extruded
@@ -27,7 +29,6 @@ struct GCodePathConfig
     bool is_bridge_path{ false }; //!< whether current config is used when bridging
     double fan_speed{ FAN_SPEED_DEFAULT }; //!< fan speed override for this path, value should be within range 0-100 (inclusive) and ignored otherwise
     double extrusion_mm3_per_mm{ calculateExtrusion() }; //!< current mm^3 filament moved per mm line traversed
-    static constexpr double FAN_SPEED_DEFAULT = -1;
 
     [[nodiscard]] constexpr bool operator==(const GCodePathConfig& other) const noexcept = default;
     [[nodiscard]] constexpr auto operator<=>(const GCodePathConfig& other) const = default;
diff --git a/src/LayerPlan.cpp b/src/LayerPlan.cpp
index a72c5b6110..56d7514509 100644
--- a/src/LayerPlan.cpp
+++ b/src/LayerPlan.cpp
@@ -1897,7 +1897,7 @@ void ExtruderPlan::processFanSpeedForMinimalLayerTime(Duration minTime, double t
 
     const double total_layer_time = estimates_.getTotalTime() + time_other_extr_plans;
     const double layer_time_diff = fan_speed_layer_time_settings_.cool_min_layer_time_fan_speed_max - minTime;
-    const double fraction_of_slope = std::clamp((total_layer_time - minTime) / layer_time_diff, 0.0, 1.0);
+    const double fraction_of_slope = (layer_time_diff != 0.0) ? std::clamp((total_layer_time - minTime) / layer_time_diff, 0.0, 1.0) : 1.0;
     fan_speed = std::lerp(fan_speed_layer_time_settings_.cool_fan_speed_max, fan_speed, fraction_of_slope);
 }