--- a/sys/libkern/flsl.c
+++ b/sys/libkern/flsl.c
@@ -34,6 +34,7 @@
 /*
  * Find Last Set bit
  */
+#if !defined(HAVE_INLINE_FLSL)
 int
 flsl(long mask)
 {
@@ -45,3 +46,4 @@
 		mask = (unsigned long)mask >> 1;
 	return (bit);
 }
+#endif