diff --git a/src/tuple.c b/src/tuple.c
index eff4bdc..9ca1f34 100644
--- a/src/tuple.c
+++ b/src/tuple.c
@@ -518,6 +518,9 @@
 	    // Add the first item to the tuple from "rettv"
 	    if (tuple_append_tv(tuple, rettv) == FAIL)
 		return FAIL;
+	    // The first item in "rettv" is added to the tuple.  Set the rettv
+	    // type to unknown, so that the caller doesn't free it.
+	    rettv->v_type = VAR_UNKNOWN;
 	}
     }