diff --git a/lib/libcxxrt/Makefile b/lib/libcxxrt/Makefile
--- a/lib/libcxxrt/Makefile
+++ b/lib/libcxxrt/Makefile
@@ -42,3 +42,13 @@
 .endif
 
 .include <bsd.lib.mk>
+
+# gcc13 doesn't support _Float16 on riscv, powerpc64, and x86 or __int128
+# on i386.  Disable checks for missing symbols to allow this to link.
+#
+# XXX: This is a hack that hides an ABI divergence between clang and gcc.
+.if ${COMPILER_TYPE} == "gcc" && \
+    (${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "i386" || \
+     ${MACHINE_ARCH:Mpowerpc64*} || ${MACHINE_ARCH} == "riscv64")
+LDFLAGS+=	-Wl,--undefined-version
+.endif