diff --git a/lib/libspl/include/assert.h b/lib/libspl/include/assert.h
index 19b25f7dd825..1b8f6befb9d5 100644
--- a/lib/libspl/include/assert.h
+++ b/lib/libspl/include/assert.h
@@ -34,7 +34,7 @@
 #include <stdarg.h>
 
 #ifndef _KERNEL
-int aok;
+extern int aok;
 #endif
 
 static inline int
diff --git a/lib/libspl/zone.c b/lib/libspl/zone.c
index 5ca93b224d9e..fb33ebaee7f8 100644
--- a/lib/libspl/zone.c
+++ b/lib/libspl/zone.c
@@ -27,6 +27,8 @@
 #include <string.h>
 #include <errno.h>
 
+int aok;
+
 zoneid_t
 getzoneid()
 {