diff --git a/widget/InputData.cpp b/widget/InputData.cpp
index 273970cf0bba..957af5d4bc3c 100644
--- a/widget/InputData.cpp
+++ b/widget/InputData.cpp
@@ -96,7 +96,8 @@ MultiTouchInput::MultiTouchInput(const WidgetTouchEvent& aTouchEvent)
                 aTouchEvent.mModifiers),
       mHandledByAPZ(aTouchEvent.mFlags.mHandledByAPZ),
       mButton(aTouchEvent.mButton),
-      mButtons(aTouchEvent.mButtons) {
+      mButtons(aTouchEvent.mButtons),
+      mInputSource(aTouchEvent.mInputSource) {
   MOZ_ASSERT(NS_IsMainThread(),
              "Can only copy from WidgetTouchEvent on main thread");
 
@@ -154,13 +155,12 @@ void MultiTouchInput::Translate(const ScreenPoint& aTranslation) {
   }
 }
 
-WidgetTouchEvent MultiTouchInput::ToWidgetEvent(nsIWidget* aWidget,
-                                                uint16_t aInputSource) const {
+WidgetTouchEvent MultiTouchInput::ToWidgetEvent(nsIWidget* aWidget) const {
   MOZ_ASSERT(NS_IsMainThread(),
              "Can only convert To WidgetTouchEvent on main thread");
-  MOZ_ASSERT(aInputSource ==
+  MOZ_ASSERT(mInputSource ==
                  mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH ||
-             aInputSource == mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_PEN);
+             mInputSource == mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_PEN);
 
   EventMessage touchEventMessage = eVoidEvent;
   switch (mType) {
@@ -192,7 +192,7 @@ WidgetTouchEvent MultiTouchInput::ToWidgetEvent(nsIWidget* aWidget,
   event.mFlags.mHandledByAPZ = mHandledByAPZ;
   event.mFocusSequenceNumber = mFocusSequenceNumber;
   event.mLayersId = mLayersId;
-  event.mInputSource = aInputSource;
+  event.mInputSource = mInputSource;
   event.mButton = mButton;
   event.mButtons = mButtons;
 
diff --git a/widget/InputData.h b/widget/InputData.h
index a7231db0e850..c167e1ecbac8 100644
--- a/widget/InputData.h
+++ b/widget/InputData.h
@@ -229,10 +229,7 @@ class MultiTouchInput : public InputData {
 
   void Translate(const ScreenPoint& aTranslation);
 
-  WidgetTouchEvent ToWidgetEvent(
-      nsIWidget* aWidget,
-      uint16_t aInputSource =
-          /* MouseEvent_Binding::MOZ_SOURCE_TOUCH = */ 5) const;
+  WidgetTouchEvent ToWidgetEvent(nsIWidget* aWidget) const;
 
   // Return the index into mTouches of the SingleTouchData with the given
   // identifier, or -1 if there is no such SingleTouchData.
@@ -252,6 +249,7 @@ class MultiTouchInput : public InputData {
   // WidgetMouseEventBase, except mButton defaults to -1 to follow PointerEvent.
   int16_t mButton = eNotPressed;
   int16_t mButtons = 0;
+  uint16_t mInputSource = /* MouseEvent_Binding::MOZ_SOURCE_TOUCH = */ 5;
 };
 
 class MouseInput : public InputData {
diff --git a/widget/nsBaseWidget.cpp b/widget/nsBaseWidget.cpp
index bb456a4141ca..74767edbd09f 100644
--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -1213,12 +1213,12 @@ class DispatchInputOnControllerThread : public Runnable {
   const APZOnly mAPZOnly;
 };
 
-void nsBaseWidget::DispatchTouchInput(MultiTouchInput& aInput,
-                                      uint16_t aInputSource) {
+void nsBaseWidget::DispatchTouchInput(MultiTouchInput& aInput) {
   MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aInputSource ==
+  MOZ_ASSERT(aInput.mInputSource ==
                  mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH ||
-             aInputSource == mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_PEN);
+             aInput.mInputSource ==
+                 mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_PEN);
   if (mAPZC) {
     MOZ_ASSERT(APZThreadUtils::IsControllerThread());
 
@@ -1227,10 +1227,10 @@ void nsBaseWidget::DispatchTouchInput(MultiTouchInput& aInput,
       return;
     }
 
-    WidgetTouchEvent event = aInput.ToWidgetEvent(this, aInputSource);
+    WidgetTouchEvent event = aInput.ToWidgetEvent(this);
     ProcessUntransformedAPZEvent(&event, result);
   } else {
-    WidgetTouchEvent event = aInput.ToWidgetEvent(this, aInputSource);
+    WidgetTouchEvent event = aInput.ToWidgetEvent(this);
 
     nsEventStatus status;
     DispatchEvent(&event, status);
diff --git a/widget/nsBaseWidget.h b/widget/nsBaseWidget.h
index 6cb2dfe87af0..285c87c49fa2 100644
--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -621,10 +621,7 @@ class nsBaseWidget : public nsIWidget, public nsSupportsWeakReference {
    * be called from the main thread, and if APZ is enabled, that must also be
    * the APZ controller thread.
    */
-  void DispatchTouchInput(
-      mozilla::MultiTouchInput& aInput,
-      uint16_t aInputSource =
-          mozilla::dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH);
+  void DispatchTouchInput(mozilla::MultiTouchInput& aInput);
 
   /**
    * Dispatch the given PanGestureInput through APZ to Gecko (if APZ is enabled)
diff --git a/widget/nsGUIEventIPC.h b/widget/nsGUIEventIPC.h
index 7e973d61200a..f72629782396 100644
--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -1099,6 +1099,7 @@ struct ParamTraits<mozilla::MultiTouchInput> {
     WriteParam(aWriter, aParam.mScreenOffset);
     WriteParam(aWriter, aParam.mButton);
     WriteParam(aWriter, aParam.mButtons);
+    WriteParam(aWriter, aParam.mInputSource);
   }
 
   static bool Read(MessageReader* aReader, paramType* aResult) {
@@ -1108,7 +1109,8 @@ struct ParamTraits<mozilla::MultiTouchInput> {
            ReadParam(aReader, &aResult->mHandledByAPZ) &&
            ReadParam(aReader, &aResult->mScreenOffset) &&
            ReadParam(aReader, &aResult->mButton) &&
-           ReadParam(aReader, &aResult->mButtons);
+           ReadParam(aReader, &aResult->mButtons) &&
+           ReadParam(aReader, &aResult->mInputSource);
   }
 };
 
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 1e56c0d1e74b..22fbaa3b5a42 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -7978,12 +7978,13 @@ bool nsWindow::DispatchTouchEventFromWMPointer(
   touchInput.mTouches.AppendElement(touchData);
   touchInput.mButton = aButton;
   touchInput.mButtons = aPointerInfo.mButtons;
+  touchInput.mInputSource = MouseEvent_Binding::MOZ_SOURCE_PEN;
 
   // POINTER_INFO.dwKeyStates can't be used as it only supports Shift and Ctrl
   ModifierKeyState modifierKeyState;
   touchInput.modifiers = modifierKeyState.GetModifiers();
 
-  DispatchTouchInput(touchInput, MouseEvent_Binding::MOZ_SOURCE_PEN);
+  DispatchTouchInput(touchInput);
   return true;
 }