diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
index 2591f176c37..20d079b1ce8 100644
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -169,7 +169,7 @@ ${OBJS}: ${_link}
 SYSDIR=	${_dir}
 .endif
 .endfor
-.if !defined(SYSDIR) || !exists(${SYSDIR}/kern)
+.if !defined(SYSDIR) || !exists(${SYSDIR}/kern/)
 .error "can't find kernel source tree"
 .endif