diff --git a/mozglue/linker/ElfLoader.cpp b/mozglue/linker/ElfLoader.cpp
index ec78122d3c80..23fbe3a897ba 100644
--- a/mozglue/linker/ElfLoader.cpp
+++ b/mozglue/linker/ElfLoader.cpp
@@ -7,6 +7,7 @@
 #include <cstdlib>
 #include <cstdio>
 #include <dlfcn.h>
+#include <optional>
 #include <unistd.h>
 #include <errno.h>
 #include <algorithm>
@@ -18,6 +19,7 @@
 #include "Logging.h"
 #include "Utils.h"
 #include <inttypes.h>
+#include "mozilla/ScopeExit.h"
 
 // From Utils.h
 mozilla::Atomic<size_t, mozilla::ReleaseAcquire> gPageSize;
@@ -152,8 +154,8 @@ class DlIteratePhdrHelper {
   DlIteratePhdrHelper() {
     int pipefd[2];
     valid_pipe = (pipe(pipefd) == 0);
-    read_fd.reset(pipefd[0]);
-    write_fd.reset(pipefd[1]);
+    read_fd.emplace(pipefd[0]);
+    write_fd.emplace(pipefd[1]);
   }
 
   int fill_and_call(dl_phdr_cb callback, const void* l_addr, const char* l_name,
@@ -161,8 +163,8 @@ class DlIteratePhdrHelper {
 
  private:
   bool valid_pipe;
-  AutoCloseFD read_fd;
-  AutoCloseFD write_fd;
+  std::optional<AutoCloseFD> read_fd;
+  std::optional<AutoCloseFD> write_fd;
 };
 
 // This function is called for each shared library iterated over by
@@ -199,7 +201,7 @@ int DlIteratePhdrHelper::fill_and_call(dl_phdr_cb callback, const void* l_addr,
     static_assert(sizeof(raw_ehdr) < PIPE_BUF, "PIPE_BUF is too small");
     do {
       // writes are atomic when smaller than PIPE_BUF, per POSIX.1-2008.
-      ret = write(write_fd, l_addr, sizeof(raw_ehdr));
+      ret = write(*write_fd, l_addr, sizeof(raw_ehdr));
     } while (ret == -1 && errno == EINTR);
     if (ret != sizeof(raw_ehdr)) {
       if (ret == -1 && errno == EFAULT) {
@@ -212,7 +214,7 @@ int DlIteratePhdrHelper::fill_and_call(dl_phdr_cb callback, const void* l_addr,
       do {
         // Per POSIX.1-2008, interrupted reads can return a length smaller
         // than the given one instead of failing with errno EINTR.
-        ret = read(read_fd, raw_ehdr + nbytes, sizeof(raw_ehdr) - nbytes);
+        ret = read(*read_fd, raw_ehdr + nbytes, sizeof(raw_ehdr) - nbytes);
         if (ret > 0) nbytes += ret;
       } while ((nbytes != sizeof(raw_ehdr) && ret > 0) ||
                (ret == -1 && errno == EINTR));
@@ -834,7 +836,10 @@ class EnsureWritable {
     /* The interesting part of the /proc/self/maps format looks like:
      * startAddr-endAddr rwxp */
     int result = 0;
-    AutoCloseFILE f(fopen("/proc/self/maps", "r"));
+    FILE* const f = fopen("/proc/self/maps", "r");
+    const auto cleanup = mozilla::MakeScopeExit([&]() {
+      if (f) fclose(f);
+    });
     while (f) {
       unsigned long long startAddr, endAddr;
       char perms[5];
diff --git a/mozglue/linker/Mappable.cpp b/mozglue/linker/Mappable.cpp
index e701928a2f98..55a7aadfcc0e 100644
--- a/mozglue/linker/Mappable.cpp
+++ b/mozglue/linker/Mappable.cpp
@@ -15,20 +15,20 @@ Mappable* Mappable::Create(const char* path) {
 
 MemoryRange Mappable::mmap(const void* addr, size_t length, int prot, int flags,
                            off_t offset) {
-  MOZ_ASSERT(fd != -1);
+  MOZ_ASSERT(fd && *fd != -1);
   MOZ_ASSERT(!(flags & MAP_SHARED));
   flags |= MAP_PRIVATE;
 
-  return MemoryRange::mmap(const_cast<void*>(addr), length, prot, flags, fd,
+  return MemoryRange::mmap(const_cast<void*>(addr), length, prot, flags, *fd,
                            offset);
 }
 
 void Mappable::finalize() {
   /* Close file ; equivalent to close(fd.forget()) */
-  fd = -1;
+  fd.emplace(-1);
 }
 
 size_t Mappable::GetLength() const {
   struct stat st;
-  return fstat(fd, &st) ? 0 : st.st_size;
+  return fstat(*fd, &st) ? 0 : st.st_size;
 }
diff --git a/mozglue/linker/Mappable.h b/mozglue/linker/Mappable.h
index d03c3334bbc4..3e25fc88c99b 100644
--- a/mozglue/linker/Mappable.h
+++ b/mozglue/linker/Mappable.h
@@ -5,6 +5,7 @@
 #ifndef Mappable_h
 #define Mappable_h
 
+#include <optional>
 #include "mozilla/RefCounted.h"
 #include "Utils.h"
 
@@ -48,7 +49,7 @@ class Mappable : public mozilla::RefCounted<Mappable> {
 
  private:
   /* File descriptor */
-  AutoCloseFD fd;
+  std::optional<AutoCloseFD> fd;
 };
 
 #endif /* Mappable_h */
diff --git a/mozglue/linker/Utils.h b/mozglue/linker/Utils.h
index d3827f1f4145..4aea454d6e65 100644
--- a/mozglue/linker/Utils.h
+++ b/mozglue/linker/Utils.h
@@ -12,7 +12,6 @@
 #include <unistd.h>
 #include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
-#include "mozilla/Scoped.h"
 
 /**
  * On architectures that are little endian and that support unaligned reads,
@@ -75,29 +74,15 @@ typedef le_to_cpu<unsigned char> le_uint16;
 typedef le_to_cpu<le_uint16> le_uint32;
 #endif
 
-/**
- * AutoCloseFD is a RAII wrapper for POSIX file descriptors
- */
-struct AutoCloseFDTraits {
-  typedef int type;
-  static int empty() { return -1; }
-  static void release(int fd) {
+struct AutoCloseFD {
+  const int fd;
+
+  MOZ_IMPLICIT AutoCloseFD(int fd) : fd(fd) {}
+  ~AutoCloseFD() {
     if (fd != -1) close(fd);
   }
+  operator int() const { return fd; }
 };
-typedef mozilla::Scoped<AutoCloseFDTraits> AutoCloseFD;
-
-/**
- * AutoCloseFILE is a RAII wrapper for POSIX streams
- */
-struct AutoCloseFILETraits {
-  typedef FILE* type;
-  static FILE* empty() { return nullptr; }
-  static void release(FILE* f) {
-    if (f) fclose(f);
-  }
-};
-typedef mozilla::Scoped<AutoCloseFILETraits> AutoCloseFILE;
 
 extern mozilla::Atomic<size_t, mozilla::ReleaseAcquire> gPageSize;