diff --git a/examples/cluster.c b/examples/cluster.c
index 52e9b7c..6af33db 100644
--- a/examples/cluster.c
+++ b/examples/cluster.c
@@ -10,34 +10,31 @@
 #include <hexagram/window.h>
 #include <hexagram/cluster.h>
 
-static hexagram_cluster_state state = {
-    0, 0, 0, 0
-};
-
-static void cluster_update(struct can_frame *frame) {
+static void cluster_update(hexagram_cluster *cluster,
+                           struct can_frame *frame) {
     switch (frame->can_id) {
         case 0x280: {
-            state.rpm = 0.25 *
+            cluster->state.rpm = 0.25 *
                 (double)(frame->data[2] | (frame->data[3] << 8));
 
             break;
         }
 
         case 0x288: {
-            state.temp = (double)(frame->data[1] - 48 * 0.75);
+            cluster->state.temp = (double)(frame->data[1] - 48 * 0.75);
 
             break;
         }
 
         case 0x320: {
-            state.fuel = (double)(frame->data[2] & 0xf) / 16.0;
+            cluster->state.fuel = (double)(frame->data[2] & 0xf) / 16.0;
 
             break;
         }
 
         case 0x5a0: {
-            state.rps = 0.001 * (double)(frame->data[1]
-                                      | (frame->data[2] << 8));
+            cluster->state.rps = 0.001 * (double)(frame->data[1]
+                                               | (frame->data[2] << 8));
 
             break;
         }
@@ -136,7 +133,7 @@ int main(int argc, char **argv) {
                 case MapNotify:
                 case Expose:
                     hexagram_window_refresh_bg(window);
-                    hexagram_cluster_draw_fg(cluster, fg, &state);
+                    hexagram_cluster_draw_fg(cluster, fg);
                     hexagram_window_swap_buffer(window);
 
                     break;
@@ -168,14 +165,14 @@ int main(int argc, char **argv) {
                 case 0x5a0: {
                     struct timeval now;
 
-                    cluster_update(&frame);
+                    cluster_update(cluster, &frame);
 
                     (void)gettimeofday(&now, NULL);
 
                     if (now.tv_sec  - last.tv_sec
                      || now.tv_usec - last.tv_usec > 16666) {
                         hexagram_window_refresh_bg(window);
-                        hexagram_cluster_draw_fg(cluster, fg, &state);
+                        hexagram_cluster_draw_fg(cluster, fg);
                         hexagram_window_swap_buffer(window);
 
                         (void)memcpy(&last, &now, sizeof(now));
diff --git a/include/hexagram/cluster.h b/include/hexagram/cluster.h
index f66c0d8..8514dc6 100644
--- a/include/hexagram/cluster.h
+++ b/include/hexagram/cluster.h
@@ -9,10 +9,6 @@
 #include <hexagram/fuel.h>
 #include <hexagram/mfd.h>
 
-typedef struct _hexagram_cluster_state {
-    double rpm, rps, temp, fuel;
-} hexagram_cluster_state;
-
 typedef struct _hexagram_cluster {
     hexagram_tacho  tacho;
     hexagram_speedo speedo;
@@ -22,6 +18,10 @@ typedef struct _hexagram_cluster {
 
     double width,
            height;
+
+    struct {
+        double rpm, rps, temp, fuel;
+    } state;
 } hexagram_cluster;
 
 hexagram_cluster *hexagram_cluster_new(double width,
@@ -31,7 +31,6 @@ void hexagram_cluster_draw_bg(hexagram_cluster *cluster,
                               cairo_t *cr);
 
 void hexagram_cluster_draw_fg(hexagram_cluster *cluster,
-                              cairo_t *cr,
-                              hexagram_cluster_state *state);
+                              cairo_t *cr);
 
 #endif /* _HEXAGRAM_CLUSTER_H */
diff --git a/src/cluster.c b/src/cluster.c
index edef543..424de0c 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -1,4 +1,5 @@
 #include <stdlib.h>
+#include <string.h>
 
 #include <hexagram/cluster.h>
 
@@ -41,6 +42,11 @@ hexagram_cluster *hexagram_cluster_new(double width, double height) {
     cluster->width  = width;
     cluster->height = height;
 
+    /*
+     * Initialize mutable state
+     */
+    memset(&cluster->state, '\0', sizeof(cluster->state));
+
     return cluster;
 
 error_malloc_cluster:
@@ -63,16 +69,15 @@ void hexagram_cluster_draw_bg(hexagram_cluster *cluster,
 }
 
 void hexagram_cluster_draw_fg(hexagram_cluster *cluster,
-                              cairo_t *cr,
-                              hexagram_cluster_state *state) {
-    hexagram_tacho_draw_needle(&cluster->tacho, cr, state->rpm);
+                              cairo_t *cr) {
+    hexagram_tacho_draw_needle(&cluster->tacho, cr, cluster->state.rpm);
 
     hexagram_speedo_draw_needle(&cluster->speedo, cr,
-                                (2.032 * state->rps * 3600) / 1000.0);
+                                (2.032 * cluster->state.rps * 3600) / 1000.0);
 
     hexagram_thermo_draw_needle(&cluster->thermo, cr,
-                                state->temp);
+                                cluster->state.temp);
 
     hexagram_fuel_draw_needle(&cluster->fuel, cr,
-                              state->fuel);
+                              cluster->state.fuel);
 }