diff --git a/audio/spectmorph/Makefile b/audio/spectmorph/Makefile
index 3ead26e0b97c..52864fa7dc7c 100644
--- a/audio/spectmorph/Makefile
+++ b/audio/spectmorph/Makefile
@@ -1,55 +1,54 @@
 PORTNAME=	spectmorph
 DISTVERSION=	0.6.0
 CATEGORIES=	audio
 MASTER_SITES=	https://github.com/swesterfeld/spectmorph/releases/download/${DISTVERSION}/
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	Analyze and combine samples of musical instruments
 WWW=		https://spectmorph.org/
 
 LICENSE=	GPLv2
 LICENSE_FILE=	${WRKSRC}/COPYING
 
 BROKEN_aarch64=	error: unknown type name '__m128'
 BROKEN_armv7=	error: unknown type name '__m128'
 
 BUILD_DEPENDS=	fftw3>0:math/fftw3
 LIB_DEPENDS=	libao.so:audio/libao \
 		libfftw3f.so:math/fftw3-float \
 		libfreetype.so:print/freetype2 \
 		libsndfile.so:audio/libsndfile
 
 USES=		autoreconf desktop-file-utils gettext gl gmake gnome iconv libtool pkgconfig python:run qt:5 shebangfix tar:bz2 xorg
 USE_QT=		core gui widgets buildtools:build
 USE_GNOME=	cairo glib20
 USE_GL=		gl
 USE_XORG=	x11
 USE_LDCONFIG=	yes
-USE_CXXSTD=	c++14 # fix compilation failure on 14: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
 
 SHEBANG_FILES=	tools/sminstbuilder.in
 
 GNU_CONFIGURE=	yes
 
 LDFLAGS+=	-L${LOCALBASE}/lib -lfftw3f_threads
 
 INSTALL_TARGET=	install-strip
 
 OPTIONS_DEFINE=		JACK LV2
 OPTIONS_DEFAULT=	JACK LV2
 OPTIONS_SUB=		yes
 
 JACK_CONFIGURE_WITH=	jack
 JACK_LIB_DEPENDS=	libjack.so:audio/jack
 
 LV2_DESC=		Build the LV2 plugin
 LV2_CONFIGURE_WITH=	lv2
 LV2_BUILD_DEPENDS=	lv2>0:audio/lv2
 
 post-install:
 	@cd ${STAGEDIR}${PREFIX} && ${STRIP_CMD} \
 		lib/vst/spectmorph_vst.so \
 		lib/clap/SpectMorph.clap \
 		lib/lv2/spectmorph.lv2/spectmorph_lv2.so
 
 .include <bsd.port.mk>
diff --git a/audio/spectmorph/files/patch-lib_smmath.hh b/audio/spectmorph/files/patch-lib_smmath.hh
new file mode 100644
index 000000000000..964a0b94fdcb
--- /dev/null
+++ b/audio/spectmorph/files/patch-lib_smmath.hh
@@ -0,0 +1,23 @@
+- fix compilation failure on 14: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
+- see https://github.com/swesterfeld/spectmorph/issues/23
+
+--- lib/smmath.hh.orig	2023-07-12 03:47:47 UTC
++++ lib/smmath.hh
+@@ -431,7 +431,7 @@ double db_from_factor (double factor, double min_dB);
+ 
+ #if defined (__i386__) && defined (__GNUC__)
+ static inline int G_GNUC_CONST
+-sm_ftoi (register float f)
++sm_ftoi (float f)
+ {
+   int r;
+ 
+@@ -441,7 +441,7 @@ sm_ftoi (register float f)
+   return r;
+ }
+ static inline int G_GNUC_CONST
+-sm_dtoi (register double f)
++sm_dtoi (double f)
+ {
+   int r;
+