Fix regression in expand_term

Terms with only a derivative count as having a derivative as operator

1 files changed, 1 insertions, 1 deletions

diff --git a/series.mac b/series.mac
index e4a42c3..581f88c 100644
--- a/series.mac
+++ b/series.mac
@@ -265,7 +265,7 @@ expand_term(expr, coeffs) := (
     expansion_order : expansion_order - lopow(d, r),
     expand(expand_term(n, coeffs) / d))
   else (
-    error(printf(false, "expand_term: invalid operator '~a'", op(expr)))));
+    apply1(__expand_term_subst(wrap_exp(expr), coeffs), r_simp_small)));
 
 
 /* Solve main equations term by term */