diff --git a/src/alloc.c b/src/alloc.c
index 7c33687ccdf..8f94d2b6097 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -430,6 +430,7 @@ XFLOAT_INIT (Lisp_Object f, double n)
   XFLOAT (f)->u.data = n;
 }
 
+#ifdef DOUG_LEA_MALLOC
 static bool
 pointers_fit_in_lispobj_p (void)
 {
@@ -446,6 +447,7 @@ mmap_lisp_allowed_p (void)
      regions.  */
   return pointers_fit_in_lispobj_p () && !might_dump;
 }
+#endif
 
 /* Head of a circularly-linked list of extant finalizers. */
 static struct Lisp_Finalizer finalizers;