diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 2e548be84e81..085ad4751448 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -3165,15 +3165,17 @@ JS_StealArrayBufferContents(JSContext *cx, JS::HandleObject obj, void **contents
 
 /*
  * Allocate memory that may be eventually passed to
- * JS_NewArrayBufferWithContents. |nbytes| is the number of payload bytes
- * required. The pointer to pass to JS_NewArrayBufferWithContents is returned
- * in |contents|. The pointer to the |nbytes| of usable memory is returned in
- * |data|. (*|contents| will contain a header before |data|.) The only legal
- * operations on *|contents| is to free it, or pass it to
- * JS_NewArrayBufferWithContents or JS_ReallocateArrayBufferContents.
+ * JS_NewArrayBufferWithContents. |maybecx| is optional; if a non-nullptr cx is
+ * given, it will be used for memory accounting and OOM reporting. |nbytes| is
+ * the number of payload bytes required. The pointer to pass to
+ * JS_NewArrayBufferWithContents is returned in |contents|. The pointer to the
+ * |nbytes| of usable memory is returned in |data|. (*|contents| will contain a
+ * header before |data|.) The only legal operations on *|contents| is to free
+ * it, or pass it to JS_NewArrayBufferWithContents or
+ * JS_ReallocateArrayBufferContents.
  */
 extern JS_PUBLIC_API(bool)
-JS_AllocateArrayBufferContents(JSContext *cx, uint32_t nbytes, void **contents, uint8_t **data);
+JS_AllocateArrayBufferContents(JSContext *maybecx, uint32_t nbytes, void **contents, uint8_t **data);
 
 /*
  * Reallocate memory allocated by JS_AllocateArrayBufferContents, growing or
diff --git a/js/src/vm/TypedArrayObject.cpp b/js/src/vm/TypedArrayObject.cpp
index e6720e59a05f..ae36dc073c7e 100644
--- a/js/src/vm/TypedArrayObject.cpp
+++ b/js/src/vm/TypedArrayObject.cpp
@@ -4088,9 +4088,10 @@ JS_NewArrayBufferWithContents(JSContext *cx, void *contents)
 }
 
 JS_PUBLIC_API(bool)
-JS_AllocateArrayBufferContents(JSContext *cx, uint32_t nbytes, void **contents, uint8_t **data)
+JS_AllocateArrayBufferContents(JSContext *maybecx, uint32_t nbytes,
+                               void **contents, uint8_t **data)
 {
-    js::ObjectElements *header = AllocateArrayBufferContents(cx, nbytes);
+    js::ObjectElements *header = AllocateArrayBufferContents(maybecx, nbytes);
     if (!header)
         return false;