diff --git a/bn.c b/bn.c
index 6526ea7..2c204cb 100644
--- a/bn.c
+++ b/bn.c
@@ -147,14 +147,22 @@ void bignum_to_string(struct bn* n, char* str, int nbytes)
     j += 1;
   }
  
-  /* Move string j places ahead, effectively skipping leading zeros */ 
-  for (i = 0; i < (nbytes - j); ++i)
+  /* Detect whether bignum is zero or not */
+  if (j == 2*BIG_NUM_BYTES)
   {
-    str[i] = str[i + j];
+    str[0] = '0';
+    str[1] = 0;
+  }
+  else
+  {
+    /* Move string j places ahead, effectively skipping leading zeros */ 
+    for (i = 0; i < (nbytes - j); ++i)
+    {
+      str[i] = str[i + j];
+    }
+    /* Zero-terminate string */
+    str[i] = 0;
   }
-
-  /* Zero-terminate string */
-  str[i] = 0;
 }
 
 
diff --git a/bn.h b/bn.h
index 940ffe7..6fd4872 100644
--- a/bn.h
+++ b/bn.h
@@ -29,8 +29,12 @@ There may well be room for performance-optimizations and improvements.
   #define WORD_SIZE 4
 #endif
 
+#ifndef BIG_NUM_BYTES
+  #define BIG_NUM_BYTES 128 
+#endif
+
 /* Size of big-numbers in bytes */
-#define BN_ARRAY_SIZE    (128 / WORD_SIZE)
+#define BN_ARRAY_SIZE    (BIG_NUM_BYTES / WORD_SIZE)
 
 
 /* Here comes the compile-time specialization for how large the underlying array size should be. */