diff --git a/pi.c b/pi.c
index 33766b1..6917899 100644
--- a/pi.c
+++ b/pi.c
@@ -29,8 +29,8 @@
 #define SWTS_KI 0.001
 
 /* These two take their values from the configuration file. (see ptp4l.c) */
-extern double configured_pi_kp;
-extern double configured_pi_ki;
+double configured_pi_kp;
+double configured_pi_ki;
 
 struct pi_servo {
 	struct servo servo;
diff --git a/pi.h b/pi.h
index aa2bd85..e1babd3 100644
--- a/pi.h
+++ b/pi.h
@@ -21,6 +21,18 @@
 
 #include "servo.h"
 
+/**
+ * When set to a non-zero value, this variable determines the
+ * proportional constant for the PI controller.
+ */
+extern double configured_pi_kp;
+
+/**
+ * When set to a non-zero value, this variable determines the
+ * integral constant for the PI controller.
+ */
+extern double configured_pi_ki;
+
 struct servo *pi_servo_create(int max_ppb, int sw_ts);
 
 #endif
diff --git a/ptp4l.c b/ptp4l.c
index a695164..6986aef 100644
--- a/ptp4l.c
+++ b/ptp4l.c
@@ -24,13 +24,13 @@
 
 #include "clock.h"
 #include "config.h"
+#include "pi.h"
 #include "print.h"
 #include "sk.h"
 #include "transport.h"
 #include "util.h"
 
 int assume_two_step;
-double configured_pi_kp, configured_pi_ki; /*see pi.c*/
 extern unsigned char ptp_dst_mac[]; /*see raw.c*/
 extern unsigned char p2p_dst_mac[]; /*see raw.c*/