diff --git a/src/runner.h b/src/runner.h
index a8caf24248c99438f16729e2cac3e1031535f62b..e7e4da40e09e949c12c7523e1cd8909c7c3db8c0 100644
--- a/src/runner.h
+++ b/src/runner.h
@@ -23,6 +23,8 @@
 #ifndef SWIFT_RUNNER_H
 #define SWIFT_RUNNER_H
 
+#include "cache.h"
+
 extern const double runner_shift[13][3];
 extern const char runner_flip[27];
 
@@ -45,6 +47,9 @@ struct runner {
 
   /*! The engine owing this runner. */
   struct engine *e;
+  
+  /*! The particle cache of this runner. */
+  struct cache par_cache;
 };
 
 /* Function prototypes. */