diff --git a/src/util/mpn.h b/src/util/mpn.h
index 7b3b392e9..45209c269 100644
--- a/src/util/mpn.h
+++ b/src/util/mpn.h
@@ -54,30 +54,7 @@ public:
     char * to_string(mpn_digit const * a, size_t lng,
                      char * buf, size_t lbuf) const;
 private:
-    #if defined(__LP64__) || defined(_WIN64)
-    class  mpn_sbuffer : public sbuffer<mpn_digit> {
-    public:
-        mpn_sbuffer() : sbuffer<mpn_digit>() {}
-
-        mpn_sbuffer(size_t nsz, const mpn_digit & elem = 0) :
-          sbuffer<mpn_digit>(static_cast<unsigned>(nsz), elem)
-        {
-        }
-        void resize(size_t nsz, const mpn_digit & elem = 0) {
-            sbuffer<mpn_digit>::resize(static_cast<unsigned>(nsz), elem);
-        }
-
-        mpn_digit & operator[](size_t idx) {
-            return sbuffer<mpn_digit>::operator[](static_cast<unsigned>(idx));
-        }
-
-        const mpn_digit & operator[](size_t idx) const {
-            return sbuffer<mpn_digit>::operator[](static_cast<unsigned>(idx));
-        }
-    };
-    #else
-    typedef sbuffer<mpn_digit> mpn_sbuffer;
-    #endif
+    using mpn_sbuffer = sbuffer<mpn_digit>;
 
     static const mpn_digit zero;
     void display_raw(std::ostream & out, mpn_digit const * a, size_t lng) const;
@@ -104,4 +81,3 @@ private:
     void trace(mpn_digit const * a, size_t lnga) const;
     void trace_nl(mpn_digit const * a, size_t lnga) const;
 };
-