diff --git a/ecdsa.h b/ecdsa.h
index d21a3855d..90c607010 100644
--- a/ecdsa.h
+++ b/ecdsa.h
@@ -48,10 +48,16 @@ typedef struct {
 
 } ecdsa_curve;
 
+// 4 byte prefix + 40 byte data (segwit)
 #define MAX_ADDR_RAW_SIZE (4 + 40)
+// bottle neck is segwit bech32:
+// 4 human readable prefix + 1 separator + 64 data + 6 checksum + 1 NUL
+// the standard says 83 characters in hrp, but currently all coins use only 2
+#define MAX_ADDR_SIZE (4+1+64+6+1)
+// 4 byte prefix + 32 byte privkey + 1 byte compressed marker
 #define MAX_WIF_RAW_SIZE (4 + 32 + 1)
-#define MAX_ADDR_SIZE (54)
-#define MAX_WIF_SIZE (58)
+// (4+32+1 + 4 [checksum]) * 8 / log2(58) plus NUL.
+#define MAX_WIF_SIZE (57)
 
 void point_copy(const curve_point *cp1, curve_point *cp2);
 void point_add(const ecdsa_curve *curve, const curve_point *cp1, curve_point *cp2);