diff --git a/sys/compat/linuxkpi/common/include/linux/kernel.h b/sys/compat/linuxkpi/common/include/linux/kernel.h
--- a/sys/compat/linuxkpi/common/include/linux/kernel.h
+++ b/sys/compat/linuxkpi/common/include/linux/kernel.h
@@ -623,12 +623,6 @@
 	return ((q * multiplier) + ((r * multiplier) / divisor));
 }
 
-static inline int64_t
-abs64(int64_t x)
-{
-	return (x < 0 ? -x : x);
-}
-
 typedef struct linux_ratelimit {
 	struct timeval lasttime;
 	int counter;
diff --git a/sys/sys/libkern.h b/sys/sys/libkern.h
--- a/sys/sys/libkern.h
+++ b/sys/sys/libkern.h
@@ -113,6 +113,7 @@
 static __inline off_t omin(off_t a, off_t b) { return (a < b ? a : b); }
 static __inline int abs(int a) { return (a < 0 ? -a : a); }
 static __inline long labs(long a) { return (a < 0 ? -a : a); }
+static __inline int64_t abs64(int64_t a) { return (a < 0 ? -a : a); }
 static __inline quad_t qabs(quad_t a) { return (a < 0 ? -a : a); }
 
 #ifndef RANDOM_FENESTRASX