Index: sys/conf/kern.mk
===================================================================
--- sys/conf/kern.mk
+++ sys/conf/kern.mk
@@ -78,6 +78,9 @@
 FORMAT_EXTENSIONS=	-Wno-format
 .elif ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
 FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
+.elif ${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} >= 60100 && \
+    ${TARGET_ARCH} == "riscv64"
+FORMAT_EXTENSIONS=	-Wno-format
 .else
 FORMAT_EXTENSIONS=	-fformat-extensions
 .endif