diff --git a/ch04.asciidoc b/ch04.asciidoc
index e59a6842..619ed8c0 100644
--- a/ch04.asciidoc
+++ b/ch04.asciidoc
@@ -24,9 +24,9 @@ An elliptic curve field is a set of points (x, y) each of which satisfies the eq
 
 y^2^ = x^3^ + ax + b (mod P)
 
-for some constants a, b and P (where P is prime). Bitcoin uses a standard curve known as secp256, where a=0, b=7, and P = 2^256^ - 2^32^ - 2^9^ - 2^8^ - 2^7^ - 2^6^ - 2^4^ - 1.
+for some constants a, b and P (where P is prime). Bitcoin uses a curve known as secp256k1, where a=0, b=7, and P = 2^256^ - 2^32^ - 2^9^ - 2^8^ - 2^7^ - 2^6^ - 2^4^ - 1.
 
-So for example, (55066263022277343669578718895168534326250603453777594175500187360389116729240, 32670510020758816978083085130507043184471273380659243275938904335757337482424) is a point on the secp256 curve. You can check this yourself using Python.
+So for example, (55066263022277343669578718895168534326250603453777594175500187360389116729240, 32670510020758816978083085130507043184471273380659243275938904335757337482424) is a point on the secp256k1 curve. You can check this yourself using Python.
 
 ----
 Python 3.4.0 (default, Mar 30 2014, 19:23:13)