--- a/vmmon/Makefile
+++ b/vmmon/Makefile
@@ -43,7 +43,11 @@ INCLUDE      += -I$(SRCROOT)/shared
 endif
 
 
+ifdef KVERSION
+VM_UNAME = $(KVERSION)
+else
 VM_UNAME = $(shell uname -r)
+endif
 
 # Header directory for the running kernel
 ifdef LINUXINCLUDE
@@ -137,7 +137,7 @@
 endif
 
 # Add Spectre options when available
-CC_OPTS += $(call vm_check_gcc,-mindirect-branch=thunk -mindirect-branch-register,)
+CC_OPTS += $(call vm_check_gcc,-mindirect-branch-register,)
 
 include $(SRCROOT)/Makefile.kernel
 
--- a/vmmon/linux/driver.c
+++ b/vmmon/linux/driver.c
@@ -38,6 +38,8 @@
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 32)
 #error Linux kernels before 2.6.32 are not supported
+#elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
+#error Linux kernels from 5.8.0 are not supported
 #endif
 
 #include <asm/io.h>