--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -842,17 +842,17 @@ nsPresContext::AppUnitsPerDevPixelChange
   InvalidatePaintedLayers();
 
   if (mDeviceContext) {
     mDeviceContext->FlushFontCache();
   }
 
   if (HasCachedStyleData()) {
     // All cached style data must be recomputed.
-    MediaFeatureValuesChanged(eRestyle_Subtree, NS_STYLE_HINT_REFLOW);
+    MediaFeatureValuesChanged(eRestyle_ForceDescendants, NS_STYLE_HINT_REFLOW);
   }
 
   mCurAppUnitsPerDevPixel = AppUnitsPerDevPixel();
 }
 
 void
 nsPresContext::PreferenceChanged(const char* aPrefName)
 {

--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -544,17 +544,18 @@ public:
   void SetTextZoom(float aZoom) {
     if (aZoom == mTextZoom)
       return;
 
     mTextZoom = aZoom;
     if (HasCachedStyleData()) {
       // Media queries could have changed, since we changed the meaning
       // of 'em' units in them.
-      MediaFeatureValuesChanged(eRestyle_Subtree, NS_STYLE_HINT_REFLOW);
+      MediaFeatureValuesChanged(eRestyle_ForceDescendants,
+                                NS_STYLE_HINT_REFLOW);
     }
   }
 
   /**
    * Get the minimum font size for the specified language. If aLanguage
    * is nullptr, then the document's language is used.  This combines
    * the language-specific global preference with the per-presentation
    * base minimum font size.
@@ -579,17 +580,18 @@ public:
   void SetBaseMinFontSize(int32_t aMinFontSize) {
     if (aMinFontSize == mBaseMinFontSize)
       return;
 
     mBaseMinFontSize = aMinFontSize;
     if (HasCachedStyleData()) {
       // Media queries could have changed, since we changed the meaning
       // of 'em' units in them.
-      MediaFeatureValuesChanged(eRestyle_Subtree, NS_STYLE_HINT_REFLOW);
+      MediaFeatureValuesChanged(eRestyle_ForceDescendants,
+                                NS_STYLE_HINT_REFLOW);
     }
   }
 
   float GetFullZoom() { return mFullZoom; }
   void SetFullZoom(float aZoom);
 
   nscoord GetAutoQualityMinFontSize() {
     return DevPixelsToAppUnits(mAutoQualityMinFontSizePixelsPref);