diff --git a/mozglue/linker/CustomElf.cpp b/mozglue/linker/CustomElf.cpp
index a8c74e86756..8e2676af44f 100644
--- a/mozglue/linker/CustomElf.cpp
+++ b/mozglue/linker/CustomElf.cpp
@@ -86,10 +86,12 @@ public:
   , mappable(mappable)
   { }
 
+private:
+  friend class GenericMappedPtr<Mappable1stPagePtr>;
   void munmap(void *buf, size_t length) {
     mappable->munmap(buf, length);
   }
-private:
+
   Mappable *mappable;
 };
 
diff --git a/mozglue/linker/Mappable.cpp b/mozglue/linker/Mappable.cpp
index 9ea6b6af9cb..657d5417182 100644
--- a/mozglue/linker/Mappable.cpp
+++ b/mozglue/linker/Mappable.cpp
@@ -206,7 +206,7 @@ public:
 #ifdef ANDROID
   ~_MappableBuffer() {
     /* Free the additional page we allocated. See _MappableBuffer::Create */
-    munmap(this + ((GetLength() + PAGE_SIZE) & ~(PAGE_SIZE - 1)), PAGE_SIZE);
+    ::munmap(this + ((GetLength() + PAGE_SIZE) & ~(PAGE_SIZE - 1)), PAGE_SIZE);
   }
 #endif
 
diff --git a/mozglue/linker/Mappable.h b/mozglue/linker/Mappable.h
index 17fec1f9ffb..14a0e157088 100644
--- a/mozglue/linker/Mappable.h
+++ b/mozglue/linker/Mappable.h
@@ -26,10 +26,16 @@ public:
 
   virtual void *mmap(const void *addr, size_t length, int prot, int flags,
                      off_t offset) = 0;
+
+private:
   virtual void munmap(void *addr, size_t length) {
     ::munmap(addr, length);
   }
+  /* Limit use of Mappable::munmap to classes that keep track of the address
+   * and size of the mapping. This allows to ignore ::munmap return value. */
+  friend class Mappable1stPagePtr;
 
+public:
   /**
    * Indicate to a Mappable instance that no further mmap is going to happen.
    */
diff --git a/mozglue/linker/Utils.h b/mozglue/linker/Utils.h
index 439843d19b8..554187e5bc7 100644
--- a/mozglue/linker/Utils.h
+++ b/mozglue/linker/Utils.h
@@ -247,6 +247,8 @@ struct MappedPtr: public GenericMappedPtr<MappedPtr>
   : GenericMappedPtr<MappedPtr>(buf, length) { }
   MappedPtr(): GenericMappedPtr<MappedPtr>() { }
 
+private:
+  friend class GenericMappedPtr<MappedPtr>;
   void munmap(void *buf, size_t length)
   {
     ::munmap(buf, length);