diff --git a/memory/build/mozjemalloc.cpp b/memory/build/mozjemalloc.cpp
index 40a7ae97c724..3053d06e06ca 100644
--- a/memory/build/mozjemalloc.cpp
+++ b/memory/build/mozjemalloc.cpp
@@ -3054,7 +3054,7 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
   // Alternatively, if the allocator is not initialized yet, the pointer
   // can't be known.
   if (!chunk || !malloc_initialized) {
-    *aInfo = {TagUnknown, nullptr, 0, 0};
+    *aInfo = {TagUnknown, nullptr, 0};
     return;
   }
 
@@ -3071,14 +3071,14 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
             &huge)
             ->Search(&key);
     if (node) {
-      *aInfo = {TagLiveHuge, node->mAddr, node->mSize, node->mArena->mId};
+      *aInfo = {TagLiveHuge, node->mAddr, node->mSize};
       return;
     }
   }
 
   // It's not a huge allocation. Check if we have a known chunk.
   if (!gChunkRTree.Get(chunk)) {
-    *aInfo = {TagUnknown, nullptr, 0, 0};
+    *aInfo = {TagUnknown, nullptr, 0};
     return;
   }
 
@@ -3088,7 +3088,7 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
   size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
   if (pageind < gChunkHeaderNumPages) {
     // Within the chunk header.
-    *aInfo = {TagUnknown, nullptr, 0, 0};
+    *aInfo = {TagUnknown, nullptr, 0};
     return;
   }
 
@@ -3109,7 +3109,7 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
     }
 
     void* pageaddr = (void*)(uintptr_t(aPtr) & ~gPageSizeMask);
-    *aInfo = {tag, pageaddr, gPageSize, chunk->arena->mId};
+    *aInfo = {tag, pageaddr, gPageSize};
     return;
   }
 
@@ -3129,20 +3129,20 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
       pageind--;
       MOZ_DIAGNOSTIC_ASSERT(pageind >= gChunkHeaderNumPages);
       if (pageind < gChunkHeaderNumPages) {
-        *aInfo = {TagUnknown, nullptr, 0, 0};
+        *aInfo = {TagUnknown, nullptr, 0};
         return;
       }
 
       mapbits = chunk->map[pageind].bits;
       MOZ_DIAGNOSTIC_ASSERT(mapbits & CHUNK_MAP_LARGE);
       if (!(mapbits & CHUNK_MAP_LARGE)) {
-        *aInfo = {TagUnknown, nullptr, 0, 0};
+        *aInfo = {TagUnknown, nullptr, 0};
         return;
       }
     }
 
     void* addr = ((char*)chunk) + (pageind << gPageSize2Pow);
-    *aInfo = {TagLiveLarge, addr, size, chunk->arena->mId};
+    *aInfo = {TagLiveLarge, addr, size};
     return;
   }
 
@@ -3157,7 +3157,7 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
   uintptr_t reg0_addr = (uintptr_t)run + run->mBin->mRunFirstRegionOffset;
   if (aPtr < (void*)reg0_addr) {
     // In the run header.
-    *aInfo = {TagUnknown, nullptr, 0, 0};
+    *aInfo = {TagUnknown, nullptr, 0};
     return;
   }
 
@@ -3173,7 +3173,7 @@ inline void MozJemalloc::jemalloc_ptr_info(const void* aPtr,
   PtrInfoTag tag =
       ((run->mRegionsMask[elm] & (1U << bit))) ? TagFreedSmall : TagLiveSmall;
 
-  *aInfo = {tag, addr, size, chunk->arena->mId};
+  *aInfo = {tag, addr, size};
 }
 
 namespace Debug {
diff --git a/memory/build/mozjemalloc_types.h b/memory/build/mozjemalloc_types.h
index 1dbaa41f7674..d447fa91687f 100644
--- a/memory/build/mozjemalloc_types.h
+++ b/memory/build/mozjemalloc_types.h
@@ -94,22 +94,22 @@ typedef struct {
 
 enum PtrInfoTag {
   // The pointer is not currently known to the allocator.
-  // 'addr', 'size', and 'arenaId' are always 0.
+  // 'addr' and 'size' are always 0.
   TagUnknown,
 
   // The pointer is within a live allocation.
-  // 'addr', 'size', and 'arenaId' describe the allocation.
+  // 'addr' and 'size' describe the allocation.
   TagLiveSmall,
   TagLiveLarge,
   TagLiveHuge,
 
   // The pointer is within a small freed allocation.
-  // 'addr', 'size', and 'arenaId' describe the allocation.
+  // 'addr' and 'size' describe the allocation.
   TagFreedSmall,
 
   // The pointer is within a freed page. Details about the original
   // allocation, including its size, are not available.
-  // 'addr', 'size', and 'arenaId' describe the page.
+  // 'addr' and 'size' describe the page.
   TagFreedPageDirty,
   TagFreedPageDecommitted,
   TagFreedPageMadvised,
@@ -121,29 +121,10 @@ enum PtrInfoTag {
 // - The number of fields is minimized.
 // - The 'tag' field unambiguously defines the meaning of the subsequent fields.
 // Helper functions are used to group together related categories of tags.
-typedef struct jemalloc_ptr_info_s {
+typedef struct {
   enum PtrInfoTag tag;
   void* addr;   // meaning depends on tag; see above
   size_t size;  // meaning depends on tag; see above
-
-#ifdef MOZ_DEBUG
-  arena_id_t arenaId;  // meaning depends on tag; see above
-#endif
-
-#ifdef __cplusplus
-  jemalloc_ptr_info_s() {}
-  jemalloc_ptr_info_s(enum PtrInfoTag tag, void* addr, size_t size,
-                      arena_id_t arenaId)
-      : tag(tag),
-        addr(addr),
-        size(size)
-#  ifdef MOZ_DEBUG
-        ,
-        arenaId(arenaId)
-#  endif
-  {
-  }
-#endif
 } jemalloc_ptr_info_t;
 
 static inline bool jemalloc_ptr_is_live(jemalloc_ptr_info_t* info) {