diff --git a/include/secp256k1.h b/include/secp256k1.h
index a287f89..de6a479 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -141,7 +141,7 @@ typedef int (*secp256k1_nonce_function_t)(
  *  In:      flags: which parts of the context to initialize.
  */
 secp256k1_context_t* secp256k1_context_create(
-    int flags
+    unsigned int flags
 ) SECP256K1_WARN_UNUSED_RESULT;
 
 /** Copies a secp256k1 context object.
diff --git a/src/secp256k1.c b/src/secp256k1.c
index dbe97d0..3baadda 100644
--- a/src/secp256k1.c
+++ b/src/secp256k1.c
@@ -57,7 +57,7 @@ struct secp256k1_context_struct {
     callback_t error_callback;
 };
 
-secp256k1_context_t* secp256k1_context_create(int flags) {
+secp256k1_context_t* secp256k1_context_create(unsigned int flags) {
     secp256k1_context_t* ret = (secp256k1_context_t*)checked_malloc(&default_error_callback, sizeof(secp256k1_context_t));
     ret->illegal_callback = default_illegal_callback;
     ret->error_callback = default_error_callback;