diff --git a/accessible/base/StyleInfo.h b/accessible/base/StyleInfo.h
index 96028e6fb48e..d1cf900e6d02 100644
--- a/accessible/base/StyleInfo.h
+++ b/accessible/base/StyleInfo.h
@@ -11,6 +11,9 @@
 #include "mozilla/ComputedStyle.h"
 
 namespace mozilla {
+namespace dom {
+class Element;
+} // namespace dom
 namespace a11y {
 
 class StyleInfo
diff --git a/layout/style/ComputedStyle.h b/layout/style/ComputedStyle.h
index 0b340ae467f9..40842040e205 100644
--- a/layout/style/ComputedStyle.h
+++ b/layout/style/ComputedStyle.h
@@ -11,13 +11,16 @@
 
 #include "nsIMemoryReporter.h"
 #include <algorithm>
+#include "mozilla/ArenaObjectID.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/RestyleLogging.h"
 #include "mozilla/ServoStyleSet.h"
+#include "mozilla/ServoTypes.h"
 #include "mozilla/ServoUtils.h"
 #include "mozilla/StyleComplexColor.h"
 #include "mozilla/CachedInheritingStyles.h"
 #include "nsCSSAnonBoxes.h"
+#include "nsCSSPseudoElements.h"
 
 // Includes nsStyleStructID.
 #include "nsStyleStructFwd.h"
@@ -66,13 +69,14 @@
 #define NS_STYLE_CONTEXT_TYPE_SHIFT        37
 
 class nsAtom;
+enum nsChangeHint : uint32_t;
+class nsIPresShell;
 class nsPresContext;
 class nsWindowSizes;
 
-namespace mozilla {
-
-enum class CSSPseudoElementType : uint8_t;
-class ComputedStyle;
+#define STYLE_STRUCT(name_) struct nsStyle##name_;
+#include "nsStyleStructList.h"
+#undef STYLE_STRUCT
 
 extern "C" {
   void Servo_ComputedStyle_AddRef(const mozilla::ComputedStyle* aStyle);
@@ -80,6 +84,11 @@ extern "C" {
   void Gecko_ComputedStyle_Destroy(mozilla::ComputedStyle*);
 }
 
+namespace mozilla {
+
+enum class CSSPseudoElementType : uint8_t;
+class ComputedStyle;
+
 /**
  * A ComputedStyle represents the computed style data for an element.  The
  * computed style data are stored in a set of structs (see nsStyleStruct.h) that
diff --git a/layout/style/ServoStyleSet.h b/layout/style/ServoStyleSet.h
index b74840b394fc..71193fddee59 100644
--- a/layout/style/ServoStyleSet.h
+++ b/layout/style/ServoStyleSet.h
@@ -8,13 +8,11 @@
 #define mozilla_ServoStyleSet_h
 
 #include "mozilla/AtomArray.h"
-#include "mozilla/EffectCompositor.h"
 #include "mozilla/EnumeratedArray.h"
 #include "mozilla/EventStates.h"
 #include "mozilla/MediaFeatureChange.h"
 #include "mozilla/PostTraversalTask.h"
 #include "mozilla/ServoBindingTypes.h"
-#include "mozilla/ServoElementSnapshot.h"
 #include "mozilla/ServoBindings.h"
 #include "mozilla/ServoUtils.h"
 #include "mozilla/StyleSheetInlines.h"
@@ -24,22 +22,28 @@
 #include "nsCSSPseudoElements.h"
 #include "nsCSSAnonBoxes.h"
 #include "nsChangeHint.h"
+#include "nsCoord.h"
 #include "nsAtom.h"
 #include "nsIMemoryReporter.h"
 #include "nsTArray.h"
 
 namespace mozilla {
+namespace css {
+class Rule;
+} // namespace css
 namespace dom {
 class Element;
+class ShadowRoot;
 } // namespace dom
-class CSSStyleSheet;
 class ServoRestyleManager;
 class ServoStyleSheet;
 struct Keyframe;
 class ServoElementSnapshotTable;
 class ComputedStyle;
 class ServoStyleRuleMap;
+class StyleSheet;
 } // namespace mozilla
+class gfxFontFeatureValueSet;
 class nsCSSCounterStyleRule;
 class nsIContent;
 class nsIDocument;
@@ -471,7 +475,7 @@ public:
                         ComputedStyle* aNewParent,
                         ComputedStyle* aNewParentIgnoringFirstLine,
                         ComputedStyle* aNewLayoutParent,
-                        Element* aElement);
+                        dom::Element* aElement);
 
 private:
   friend class AutoSetInServoTraversal;
diff --git a/layout/style/StreamLoader.h b/layout/style/StreamLoader.h
index 825106c1291a..924685d3732f 100644
--- a/layout/style/StreamLoader.h
+++ b/layout/style/StreamLoader.h
@@ -7,6 +7,7 @@
 #ifndef mozilla_css_StreamLoader_h
 #define mozilla_css_StreamLoader_h
 
+#include "nsIStreamListener.h"
 #include "nsString.h"
 #include "mozilla/css/SheetLoadData.h"
 
diff --git a/modules/libpref/Preferences.cpp b/modules/libpref/Preferences.cpp
index fc80a3e4950d..47a6a79790df 100644
--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -29,6 +29,7 @@
 #include "mozilla/ServoStyleSet.h"
 #include "mozilla/StaticPrefs.h"
 #include "mozilla/SyncRunnable.h"
+#include "mozilla/SystemGroup.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/UniquePtrExtensions.h"
 #include "mozilla/URLPreloader.h"