diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3267421..6a3e2eb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 
 ## Unreleased
+- Fixed SystemHeat part-action-window fields flickering when system flux changes.
 - Improved performance
   - Color animations no longer update all materials when they haven't changed.
 
diff --git a/Source/Modules/ModuleSystemHeat.cs b/Source/Modules/ModuleSystemHeat.cs
index 600032b..f73d39e 100644
--- a/Source/Modules/ModuleSystemHeat.cs
+++ b/Source/Modules/ModuleSystemHeat.cs
@@ -293,17 +293,10 @@ protected void Update()
 
       SystemFluxUI = String.Format("{0}W", Utils.ToSI(totalSystemFlux, "F0"));
       LoopTemperatureUI = String.Format("{0:F0} / {1:F0} K", currentLoopTemperature, nominalLoopTemperature);
-      if (totalSystemFlux > 0f)
-      {
-        Fields["SystemTemperatureUI"].guiActive = true;
-        Fields["SystemTemperatureUI"].guiActiveEditor = true;
-        SystemTemperatureUI = String.Format("{0:F0} K", totalSystemTemperature);
-      }
-      else
-      {
-        Fields["SystemTemperatureUI"].guiActive = false;
-        Fields["SystemTemperatureUI"].guiActiveEditor = false;
-      }
+      // Keep the PAW layout stable when flux briefly reaches zero or changes sign.
+      // Visibility is controlled by SetSystemHeatModuleEnabled, not by the
+      // instantaneous value being displayed.
+      SystemTemperatureUI = String.Format("{0:F0} K", totalSystemTemperature);
     }
 
     protected void FindSimulator()