diff --git a/mfbt/RefPtr.h b/mfbt/RefPtr.h
index 47cfac2fecf8..5237f59f11f1 100644
--- a/mfbt/RefPtr.h
+++ b/mfbt/RefPtr.h
@@ -19,6 +19,7 @@ class nsCOMPtr_helper;
 
 namespace mozilla {
 template<class T> class OwningNonNull;
+template<class T> class StaticRefPtr;
 
 // Traditionally, RefPtr supports automatic refcounting of any pointer type
 // with AddRef() and Release() methods that follow the traditional semantics.
@@ -148,6 +149,10 @@ public:
   template<class U>
   MOZ_IMPLICIT RefPtr(const mozilla::OwningNonNull<U>& aOther);
 
+  // Defined in StaticPtr.h
+  template<class U>
+  MOZ_IMPLICIT RefPtr(const mozilla::StaticRefPtr<U>& aOther);
+
   // Assignment operators
 
   RefPtr<T>&
@@ -208,6 +213,11 @@ public:
   RefPtr<T>&
   operator=(const mozilla::OwningNonNull<U>& aOther);
 
+  // Defined in StaticPtr.h
+  template<class U>
+  RefPtr<T>&
+  operator=(const mozilla::StaticRefPtr<U>& aOther);
+
   // Other pointer operators
 
   void
diff --git a/xpcom/base/StaticPtr.h b/xpcom/base/StaticPtr.h
index 21109e709d18..f2c820a93937 100644
--- a/xpcom/base/StaticPtr.h
+++ b/xpcom/base/StaticPtr.h
@@ -7,8 +7,10 @@
 #ifndef mozilla_StaticPtr_h
 #define mozilla_StaticPtr_h
 
+#include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
 
 namespace mozilla {
 
@@ -110,6 +112,26 @@ public:
     return (this = aRhs.mRawPtr);
   }
 
+  StaticRefPtr<T>& operator=(already_AddRefed<T>& aRhs)
+  {
+    AssignAssumingAddRef(aRhs.take());
+    return *this;
+  }
+
+  StaticRefPtr<T>& operator=(already_AddRefed<T>&& aRhs)
+  {
+    AssignAssumingAddRef(aRhs.take());
+    return *this;
+  }
+
+  already_AddRefed<T>
+  forget()
+  {
+    T* temp = mRawPtr;
+    mRawPtr = nullptr;
+    return already_AddRefed<T>(temp);
+  }
+
   T* get() const { return mRawPtr; }
 
   operator T*() const { return get(); }
@@ -232,4 +254,17 @@ REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, StaticPtr_internal::Zero*,
 
 } // namespace mozilla
 
+// Declared in mozilla/RefPtr.h
+template<class T> template<class U>
+RefPtr<T>::RefPtr(const mozilla::StaticRefPtr<U>& aOther)
+  : RefPtr(aOther.get())
+{}
+
+template<class T> template<class U>
+RefPtr<T>&
+RefPtr<T>::operator=(const mozilla::StaticRefPtr<U>& aOther)
+{
+  return operator=(aOther.get());
+}
+
 #endif