DDD 3.3.12 (i386-apple-darwin16.3.0) gets Xt error

Attempting to use ddd for first time on Mac OS X 10.12.3 (using XQuartz for
X11).  Installed using Homebrew via "brew install ddd".

in Terminal:
$ ddd ./ex1

Log file:
GNU DDD 3.3.12 (i386-apple-darwin16.3.0)
Copyright (C) 1995-1999 Technische Universit?t Braunschweig, Germany.
Copyright (C) 1999-2001 Universit?t Passau, Germany.
Copyright (C) 2001 Universit?t des Saarlandes, Germany.
Copyright (C) 2001-2009 Free Software Foundation, Inc.

Compiled with GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)
Requires X11R6, Xt11R6, Motif 2.3.6 (Motif Version 2.3.6)
Includes XPM 3.4.11, Athena Panner (7000002L), Manual, App defaults, DDD
core
Built 2017-01-27 by (unknown).
$  ddd ./ex1
!  Xt error: Unresolved inheritance operation
!  Xt error
!  Cannot save options

env:
DISPLAY=/private/tmp/com.apple.launchd.4kQ4URw0Qa/org.macosforge.xquartz:0

Any help would be appreciated!

Cameron