diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index c2f6d68..c6e9d26 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -69,14 +69,14 @@
  * \param ctx       GCM context to be initialized
  * \param cipher    cipher to use (a 128-bit block cipher)
  * \param key       encryption key
- * \param keysize   must be 128, 192 or 256
+ * \param keybits   must be 128, 192 or 256
  *
  * \return          0 if successful, or a cipher specific error code
  */
 int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
                         mbedtls_cipher_id_t cipher,
                         const unsigned char *key,
-                        unsigned int keysize );
+                        unsigned int keybits );
 
 /**
  * \brief           GCM buffer encryption/decryption using a block cipher