diff --git a/src/core/core-command.c b/src/core/core-command.c
index 9372215cb..e2ad79b61 100644
--- a/src/core/core-command.c
+++ b/src/core/core-command.c
@@ -7118,7 +7118,9 @@ COMMAND_CALLBACK(set)
 
 COMMAND_CALLBACK(sys)
 {
+#ifdef HAVE_MALLOC_TRIM
     long size;
+#endif
     int num_processes;
 
     /* make C compiler happy */