diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index f2c7a814..2b3eb176 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -851,7 +851,7 @@ typedef struct {
   // TODO: digits (implicit, after object??)
 } bignum2_type;
 
-#define C_bignum_digits(n) ((((bignum2_type *)n)->sign) + 1)
+#define C_bignum_digits(n) (&(((bignum2_type *)n)->sign) + 1)
 
 // TODO: covert applicable definitions below -
 // #ifdef C_SIXTY_FOUR
diff --git a/runtime.c b/runtime.c
index 4b61360e..314db984 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2427,7 +2427,7 @@ int bignum2_num_digits(bignum2_type *bn, int radix)
   int len = bn->num_digits - 1; //C_bignum_size(num)-1;
 
   int nbits  = (size_t)len * 32; //C_BIGNUM_DIGIT_LENGTH;
-  nbits += nlz(C_bignum_digits(bn)+len); // TODO: ?
+  nbits += nlz(C_bignum_digits(bn)[len]); // TODO: ?
 
   len = nlz(radix)-1;
   len = (nbits + len - 1) / len;
@@ -2463,8 +2463,24 @@ static uint32_t bignum_digits_destructive_scale_down(uint32_t *start, uint32_t *
 void bignum2string(void *data, object cont, bignum2_type *bn, int radix)
 {
   static char *characters = "0123456789abcdef";
-  // buf
   int negp = bn->sign, radix_shift = nlz(radix) - 1;
+  int str_length = bignum2_num_digits(bn, radix);
+  int heap_grown;
+  string_type s = gc_alloc(((gc_thread_data *)data)->heap, 
+                       sizeof(string_type) + str_length + 1,
+                       boolean_f, // OK to populate manually over here
+                       (gc_thread_data *)data, 
+                       &heap_grown);
+          ((string_type *) s)->hdr.mark = ((gc_thread_data *)data)->gc_alloc_color;
+          ((string_type *) s)->hdr.grayed = 0;
+          ((string_type *) s)->hdr.immutable = 0;
+          ((string_type *) s)->tag = string_tag; 
+          ((string_type *) s)->str_length = str_length;
+          ((string_type *) s)->num_cp = str_length;
+          ((string_type *) s)->str = (((char *)s) + sizeof(string_type));
+  char *buf = string_str(s), 
+       *index = buf;  TODO: should be at other end of buf, I think??
+
   printf("DEBUG string length %d\n", bignum2_num_digits(bn, radix));
   printf("DEBUG radix=%d, nlz = %d\n", radix, radix_shift);
   printf(" DEBUG power of 2 %d\n", ((uint32_t)1 << radix_shift));
@@ -2524,6 +2540,8 @@ void bignum2string(void *data, object cont, bignum2_type *bn, int radix)
 //    }
   }
   // TODO: call into cont with string
+  printf("string is %s\n", string_str(s));
+  return_closcall1(data, k, s); 
 }
 
 object Cyc_symbol2string(void *data, object cont, object sym)
diff --git a/test-bn.scm b/test-bn.scm
index 96387bbc..6c023692 100644
--- a/test-bn.scm
+++ b/test-bn.scm
@@ -1,12 +1,13 @@
-; /sync.sh runtime.c gc.c include/cyclone/*.h test-bn.scm && cd ../cyclone-bootstrap && rm -f cyclone libcyclone.a ; make cyclone && ./cyclone -L. -I. test-bn.scm && ./test-bn && cd ../cyclone
+; ./sync.sh runtime.c gc.c include/cyclone/*.h test-bn.scm && cd ../cyclone-bootstrap && rm -f cyclone libcyclone.a ; ./install.sh && ./cyclone -L. -I. test-bn.scm && ./test-bn && cd ../cyclone
 (import (scheme base) (scheme write) (scheme repl))
 
  (define-c test-bn
    "(void *data, int argc, closure _, object k, object fx)"
    " object bn = Cyc_int2bignum2(data, obj_obj2int(fx));
      bignum2string(data, k, bn, 10);
-     return_closcall1(data, k, bn); ")
+     ")
 
 (test-bn 10)
-(test-bn 16)
+(test-bn 163264)
+(test-bn 16326)
  ;(repl)