diff --git a/Xext/sync.c b/Xext/sync.c
index 8eec01ebb..61bd693e8 100644
--- a/Xext/sync.c
+++ b/Xext/sync.c
@@ -2620,9 +2620,11 @@ IdleTimeQueryValue(void *pCounter, int64_t *pValue_return)
     int deviceid;
     CARD32 idle;
 
+    *pValue_return = 0;
     if (pCounter) {
         SyncCounter *counter = pCounter;
         IdleCounterPriv *priv = SysCounterGetPrivate(counter);
+        BUG_RETURN(priv == NULL);
         deviceid = priv->deviceid;
     }
     else
@@ -2636,6 +2638,7 @@ IdleTimeBlockHandler(void *pCounter, void *wt)
 {
     SyncCounter *counter = pCounter;
     IdleCounterPriv *priv = SysCounterGetPrivate(counter);
+    BUG_RETURN(priv == NULL);
     int64_t *less = priv->value_less;
     int64_t *greater = priv->value_greater;
     int64_t idle, old_idle;
@@ -2726,6 +2729,7 @@ IdleTimeWakeupHandler(void *pCounter, int rc)
 {
     SyncCounter *counter = pCounter;
     IdleCounterPriv *priv = SysCounterGetPrivate(counter);
+    BUG_RETURN(priv == NULL);
     int64_t *less = priv->value_less;
     int64_t *greater = priv->value_greater;
     int64_t idle;
@@ -2759,6 +2763,7 @@ IdleTimeBracketValues(void *pCounter, int64_t *pbracket_less,
 {
     SyncCounter *counter = pCounter;
     IdleCounterPriv *priv = SysCounterGetPrivate(counter);
+    BUG_RETURN(priv == NULL);
     int64_t *less = priv->value_less;
     int64_t *greater = priv->value_greater;
     Bool registered = (less || greater);