diff --git a/pi.c b/pi.c
index 9b3b09e..5fbce38 100644
--- a/pi.c
+++ b/pi.c
@@ -38,8 +38,8 @@ double configured_pi_offset = 0.0;
 
 struct pi_servo {
 	struct servo servo;
-	double offset[2];
-	double local[2];
+	int64_t offset[2];
+	uint64_t local[2];
 	double drift;
 	double maxppb;
 	double kp;
@@ -55,8 +55,8 @@ static void pi_destroy(struct servo *servo)
 }
 
 static double pi_sample(struct servo *servo,
-			double offset,
-			double local_ts,
+			int64_t offset,
+			uint64_t local_ts,
 			enum servo_state *state)
 {
 	double ki_term, ppb = 0.0;
diff --git a/servo.c b/servo.c
index 97c2e60..a312ad1 100644
--- a/servo.c
+++ b/servo.c
@@ -35,8 +35,8 @@ void servo_destroy(struct servo *servo)
 }
 
 double servo_sample(struct servo *servo,
-		    double offset,
-		    double local_ts,
+		    int64_t offset,
+		    uint64_t local_ts,
 		    enum servo_state *state)
 {
 	return servo->sample(servo, offset, local_ts, state);
diff --git a/servo.h b/servo.h
index 0d2ab71..4d4a8e7 100644
--- a/servo.h
+++ b/servo.h
@@ -20,6 +20,8 @@
 #ifndef HAVE_SERVO_H
 #define HAVE_SERVO_H
 
+#include <stdint.h>
+
 /** Opaque type */
 struct servo;
 
@@ -80,8 +82,8 @@ void servo_destroy(struct servo *servo);
  * @return The clock adjustment in parts per billion.
  */
 double servo_sample(struct servo *servo,
-		    double offset,
-		    double local_ts,
+		    int64_t offset,
+		    uint64_t local_ts,
 		    enum servo_state *state);
 
 #endif
diff --git a/servo_private.h b/servo_private.h
index 2c710e5..f9c151f 100644
--- a/servo_private.h
+++ b/servo_private.h
@@ -26,7 +26,7 @@ struct servo {
 	void (*destroy)(struct servo *servo);
 
 	double (*sample)(struct servo *servo,
-			 double offset, double local_ts,
+			 int64_t offset, uint64_t local_ts,
 			 enum servo_state *state);
 };