diff --git a/src/secp256k1/CMakeLists.txt b/src/secp256k1/CMakeLists.txt
--- a/src/secp256k1/CMakeLists.txt
+++ b/src/secp256k1/CMakeLists.txt
@@ -252,7 +252,7 @@
 endif()
 
 # Endomorphism
-option(SECP256K1_ENABLE_ENDOMORPHISM "Enable endomorphism" OFF)
+option(SECP256K1_ENABLE_ENDOMORPHISM "Enable endomorphism" ON)
 if(SECP256K1_ENABLE_ENDOMORPHISM)
 	set(USE_ENDOMORPHISM 1)
 endif()
diff --git a/src/secp256k1/src/modules/schnorr/schnorr_impl.h b/src/secp256k1/src/modules/schnorr/schnorr_impl.h
--- a/src/secp256k1/src/modules/schnorr/schnorr_impl.h
+++ b/src/secp256k1/src/modules/schnorr/schnorr_impl.h
@@ -105,7 +105,7 @@
     const unsigned char *msg32
 ) {
     int overflow = 0;
-    size_t size;
+    size_t size = 0;
     secp256k1_sha256 sha;
     unsigned char buf[33];
     secp256k1_sha256_initialize(&sha);