diff --git a/libc/arch-arm/bionic/ffs.S b/libc/arch-arm/bionic/ffs.S
index 13bd169..a3a1ea1 100644
--- a/libc/arch-arm/bionic/ffs.S
+++ b/libc/arch-arm/bionic/ffs.S
@@ -29,6 +29,7 @@
  */
 
 #include <machine/asm.h>
+#include <machine/cpu-features.h>
 
 /*
  * ffs - find first set bit, this algorithm isolates the first set