diff --git a/NEWS b/NEWS
index 81c4cbcdf..57a22fc8f 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,10 @@ Any uppercase BUG_* names are modernish shell bug IDs.
     (unset PATH; PATH=/dev/null; ls); : wrongly ran 'ls'
     (unset LC_ALL; LC_ALL=badlocale); : failed to print a diagnostic
 
+- Fix crashes on some systems, including at least a crash in 'print -v' on
+  macOS, by eliminating an invalid/undefined use of memccpy() on overlapping
+  buffers in the commonly used sfputr() function.
+
 2020-06-04:
 
 - Fix BUG_KBGPID: the $! special parameter was not set if a background job
diff --git a/src/lib/libast/sfio/sfputr.c b/src/lib/libast/sfio/sfputr.c
index 21bfb0aeb..0d0f65124 100644
--- a/src/lib/libast/sfio/sfputr.c
+++ b/src/lib/libast/sfio/sfputr.c
@@ -105,16 +105,15 @@ int		rc;	/* record separator.	*/
 			break;
 		}
 
-#if _lib_memccpy && !__ia64 /* these guys may never get it right */
-		if((ps = (uchar*)memccpy(ps,s,'\0',p)) != NIL(uchar*))
-			ps -= 1;
-		else	ps  = f->next+p;
-		s += ps - f->next;
-#else
+		/*
+		 * Do not replace the following loop with memccpy(). The
+		 * 'ps' and 's' buffers may overlap or even point to the
+		 * same buffer. See: https://github.com/att/ast/issues/78
+		 */
 		for(; p > 0; --p, ++ps, ++s)
 			if((*ps = *s) == 0)
 				break;
-#endif
+
 		w += ps - f->next;
 		f->next = ps;
 	}