diff --git a/src/patrix/Cache.h b/src/patrix/Cache.h
index c6630e9..7355ef7 100644
--- a/src/patrix/Cache.h
+++ b/src/patrix/Cache.h
@@ -26,7 +26,7 @@ private:
 
   void clearWriteEntry() {
     for (double& value: r->data) {
-      value = 0;
+      value = NAN;
     }
   }