diff --git a/lib/src/geneval.c b/lib/src/geneval.c
index f015f5600..12e1031e7 100644
--- a/lib/src/geneval.c
+++ b/lib/src/geneval.c
@@ -4387,9 +4387,22 @@ static NODE *matrix_fill_func (NODE *l, NODE *r, int f, parser *p)
     int cols = 0, rows = node_get_int(l, p);
     NODE *ret = NULL;
 
-    if (!p->err) {
-	cols = (f == F_IMAT)? rows : node_get_int(r, p);
-    }
+	if (!p->err) {
+		if (f == F_IMAT) {
+			cols = rows;
+		} else if (f == F_ZEROS || f == F_ONES || f == F_MUNIF || f == F_MNORM) {
+			cols = 1;
+			/* the r node may be absent (which means one column), but if present
+			it should hold a scalar */
+			if (!empty_or_num(r)) {
+				node_type_error(f, 2, NUM, r, p);
+			} else if (!null_or_empty(r)) {
+				cols = node_get_int(r, p);
+			}
+		} else {	/* anything actually going into this branch? */
+			cols = node_get_int(r, p);
+		}
+	}
 
     if (!p->err && !ok_matrix_dim(rows, cols, f)) {
 	p->err = E_INVARG;
@@ -15733,7 +15746,7 @@ static NODE *eval (NODE *t, parser *p)
     case F_MUNIF:
     case F_MNORM:
 	/* matrix-creation functions */
-	if (scalar_node(l) && (r == NULL || scalar_node(r))) {
+	if (scalar_node(l) && (null_or_empty(r) || scalar_node(r))) { /* was r == NULL */
 	    ret = matrix_fill_func(l, r, t->t, p);
 	} else if (!scalar_node(l)) {
 	    node_type_error(t->t, 1, NUM, l, p);