diff --git a/src/nmod_poly.h b/src/nmod_poly.h
index 72817f4fc8..cb9a889f5c 100644
--- a/src/nmod_poly.h
+++ b/src/nmod_poly.h
@@ -206,18 +206,14 @@ void nmod_poly_one(nmod_poly_t res)
     res->coeffs[0] = 1;
 }
 
+void nmod_poly_set_trunc(nmod_poly_t res, const nmod_poly_t poly, slong len);
+
 NMOD_POLY_INLINE
 void nmod_poly_truncate(nmod_poly_t poly, slong len)
 {
-    if (poly->length > len)
-    {
-        poly->length = len;
-        _nmod_poly_normalise(poly);
-    }
+    nmod_poly_set_trunc(poly, poly, len);
 }
 
-void nmod_poly_set_trunc(nmod_poly_t res, const nmod_poly_t poly, slong n);
-
 void _nmod_poly_reverse(mp_ptr output, mp_srcptr input, slong len, slong m);
 void nmod_poly_reverse(nmod_poly_t output, const nmod_poly_t input, slong m);
 
diff --git a/src/nmod_poly/set_trunc.c b/src/nmod_poly/set_trunc.c
index 24572b3b82..ee220aa950 100644
--- a/src/nmod_poly/set_trunc.c
+++ b/src/nmod_poly/set_trunc.c
@@ -13,17 +13,21 @@
 #include "nmod_poly.h"
 
 void
-nmod_poly_set_trunc(nmod_poly_t res, const nmod_poly_t poly, slong n)
+nmod_poly_set_trunc(nmod_poly_t res, const nmod_poly_t poly, slong len)
 {
     if (poly == res)
     {
-        nmod_poly_truncate(res, n);
+        if (res->length > len)
+        {
+            res->length = len;
+            _nmod_poly_normalise(res);
+        }
     }
     else
     {
         slong rlen;
 
-        rlen = FLINT_MIN(n, poly->length);
+        rlen = FLINT_MIN(len, poly->length);
         while (rlen > 0 && poly->coeffs[rlen - 1] == 0)
             rlen--;