diff --git a/dom/base/nsWindowMemoryReporter.cpp b/dom/base/nsWindowMemoryReporter.cpp
index daa97ed1847a..614e2255fda9 100644
--- a/dom/base/nsWindowMemoryReporter.cpp
+++ b/dom/base/nsWindowMemoryReporter.cpp
@@ -310,6 +310,11 @@ CollectWindowReports(nsGlobalWindow *aWindow,
               "other 'dom/' numbers.");
   aWindowTotalSizes->mDOMOtherSize += windowSizes.mDOMOtherSize;
 
+  REPORT_SIZE("/proto-iface-cache", windowSizes.mProtoIfaceCacheSize,
+              "Memory used for prototype and interface binding caches "
+              "with a window.");
+  aWindowTotalSizes->mProtoIfaceCacheSize += windowSizes.mProtoIfaceCacheSize;
+
   REPORT_SIZE("/property-tables",
               windowSizes.mPropertyTablesSize,
               "Memory used for the property tables within a window.");
@@ -531,6 +536,9 @@ nsWindowMemoryReporter::CollectReports(nsIMemoryReporterCallback* aCb,
   REPORT("window-objects/dom/other", windowTotalSizes.mDOMOtherSize,
          "This is the sum of all windows' 'dom/other' numbers.");
 
+  REPORT("window-objects/proto-iface-cache", windowTotalSizes.mProtoIfaceCacheSize,
+         "This is the sum of all windows' 'proto-iface-cache' numbers.");
+
   REPORT("window-objects/property-tables",
          windowTotalSizes.mPropertyTablesSize,
          "This is the sum of all windows' 'property-tables' numbers.");
diff --git a/dom/base/nsWindowMemoryReporter.h b/dom/base/nsWindowMemoryReporter.h
index 1691a21402b6..5a7e1ab11644 100644
--- a/dom/base/nsWindowMemoryReporter.h
+++ b/dom/base/nsWindowMemoryReporter.h
@@ -40,6 +40,7 @@ class nsWindowSizes {
   macro(Other, mLayoutTextRunsSize) \
   macro(Other, mLayoutPresContextSize) \
   macro(Other, mPropertyTablesSize) \
+  macro(Other, mProtoIfaceCacheSize) \
 
 public:
   nsWindowSizes(mozilla::MallocSizeOf aMallocSizeOf)