diff -up asymptote-2.52/prc/PRCdouble.h.s390x asymptote-2.52/prc/PRCdouble.h
--- asymptote-2.52/prc/PRCdouble.h.s390x	2019-08-10 07:22:59.805272041 -0400
+++ asymptote-2.52/prc/PRCdouble.h	2019-08-10 07:27:18.130760904 -0400
@@ -133,7 +133,7 @@ int stCOFDOECompare(const void*,const vo
 
 #ifdef WORDS_BIGENDIAN
 #ifndef HAVE_MEMRCHR
-void *memrchr(const void *,int,size_t);
+const void *memrchr(const void *,int,size_t);
 #endif
 #endif