diff --git a/gfx/layers/ipc/SharedBufferManagerParent.cpp b/gfx/layers/ipc/SharedBufferManagerParent.cpp
index 7f7a25a6b302..be39f6426d1d 100644
--- a/gfx/layers/ipc/SharedBufferManagerParent.cpp
+++ b/gfx/layers/ipc/SharedBufferManagerParent.cpp
@@ -42,7 +42,7 @@ public:
   NS_DECL_ISUPPORTS
 
   NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
-                            nsISupports* aData, bool aAnonymize)
+                            nsISupports* aData, bool aAnonymize) override
   {
     if (SharedBufferManagerParent::sManagerMonitor) {
       SharedBufferManagerParent::sManagerMonitor->Lock();
diff --git a/gfx/thebes/gfxWindowsPlatform.cpp b/gfx/thebes/gfxWindowsPlatform.cpp
index 2cd555492bd8..d180c4ac6b46 100755
--- a/gfx/thebes/gfxWindowsPlatform.cpp
+++ b/gfx/thebes/gfxWindowsPlatform.cpp
@@ -126,7 +126,7 @@ public:
     NS_DECL_ISUPPORTS
 
     NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
-                              nsISupports* aData, bool aAnonymize)
+                              nsISupports* aData, bool aAnonymize) override
     {
         nsresult rv;
 
@@ -184,7 +184,7 @@ public:
 
     NS_IMETHOD
     CollectReports(nsIMemoryReporterCallback* aCb,
-                   nsISupports* aClosure, bool aAnonymize)
+                   nsISupports* aClosure, bool aAnonymize) override
     {
         HANDLE ProcessHandle = GetCurrentProcess();
 
diff --git a/xpcom/base/AvailableMemoryTracker.cpp b/xpcom/base/AvailableMemoryTracker.cpp
index 4de029a1694c..90ed69c2d0bd 100644
--- a/xpcom/base/AvailableMemoryTracker.cpp
+++ b/xpcom/base/AvailableMemoryTracker.cpp
@@ -344,7 +344,7 @@ public:
   NS_DECL_ISUPPORTS
 
   NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
-                            nsISupports* aData, bool aAnonymize)
+                            nsISupports* aData, bool aAnonymize) override
   {
     nsresult rv;