diff --git a/share/mk/src.sys.mk b/share/mk/src.sys.mk
--- a/share/mk/src.sys.mk
+++ b/share/mk/src.sys.mk
@@ -33,11 +33,6 @@
 .endif # SRCCONF
 .endif
 
-# The following should be removed no earlier than LLVM11 being imported into the
-# tree, to ensure we don't regress the build.  LLVM11 and GCC10 will switch the
-# default over to -fno-common, making this redundant.
-CFCOMMONFLAG?=	-fno-common
-CFLAGS+=	${CFCOMMONFLAG}
 .if defined(PACKAGE_BUILDING)
 CFLAGS+=	-fmacro-prefix-map=${SRCTOP}=/usr/src -fdebug-prefix-map=${SRCTOP}=/usr/src
 .endif
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -82,10 +82,6 @@
 CFLAGS.gcc+=${CFLAGS_ARCH_PARAMS}
 .endif
 WERROR?=	-Werror
-# The following should be removed no earlier than LLVM11 being imported into the
-# tree, to ensure we don't regress the build.  LLVM11 and GCC10 will switch the
-# default over to -fno-common, making this redundant.
-CFLAGS+=	-fno-common
 
 # XXX LOCORE means "don't declare C stuff" not "for locore.s".
 ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS} ${ASM_CFLAGS.${.IMPSRC:T}}
diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -141,13 +141,6 @@
 
 # Disallow common variables, and if we end up with commons from
 # somewhere unexpected, allocate storage for them in the module itself.
-#
-# -fno-common is the default for src builds, but this should be left in place
-# until at least we catch up to GCC10/LLVM11 or otherwise enable -fno-common
-# in <bsd.sys.mk> instead.  For now, we will have duplicate -fno-common in
-# CFLAGS for in-tree module builds as they will also pick it up from
-# share/mk/src.sys.mk, but the following is important for out-of-tree modules
-# (e.g. ports).
 CFLAGS+=	-fno-common
 .if ${LINKER_TYPE} != "lld" || ${LINKER_VERSION} < 140000
 # lld >= 14 warns that -d is deprecated, and will be removed.