diff --git a/src/eval.c b/src/eval.c
index 9ef3128..bb402de 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2679,6 +2679,9 @@
     return OK;
 }
 
+/*
+ * Make a copy of blob "tv1" and append blob "tv2".
+ */
     void
 eval_addblob(typval_T *tv1, typval_T *tv2)
 {
@@ -2699,6 +2702,9 @@
     }
 }
 
+/*
+ * Make a copy of list "tv1" and append list "tv2".
+ */
     int
 eval_addlist(typval_T *tv1, typval_T *tv2)
 {
@@ -2777,8 +2783,10 @@
 #ifdef FEAT_FLOAT
 		&& (op == '.' || rettv->v_type != VAR_FLOAT)
 #endif
-		)
+		&& evaluate)
 	{
+	    int		error = FALSE;
+
 	    // For "list + ...", an illegal use of the first operand as
 	    // a number cannot be determined before evaluating the 2nd
 	    // operand: if this is also a list, all is ok.
@@ -2786,7 +2794,9 @@
 	    // we know that the first operand needs to be a string or number
 	    // without evaluating the 2nd operand.  So check before to avoid
 	    // side effects after an error.
-	    if (evaluate && tv_get_string_chk(rettv) == NULL)
+	    if (op != '.')
+		tv_get_number_chk(rettv, &error);
+	    if ((op == '.' && tv_get_string_chk(rettv) == NULL) || error)
 	    {
 		clear_tv(rettv);
 		return FAIL;