diff --git a/base64.h b/base64.h
index 1e1c7ed52e3523dcd294c2fafbfffbf7ea8ef5bf..6ca0f1c85b2e97a1bf1f8f7ab02000f774e5c4e1 100644
--- a/base64.h
+++ b/base64.h
@@ -81,7 +81,7 @@ base64_encode_update(struct base64_encode_ctx *ctx,
 		     const uint8_t *src);
 
 /* DST should point to an area of size at least
- * BASE64_ENCODE_FINAL_SIZE */
+ * BASE64_ENCODE_FINAL_LENGTH */
 unsigned
 base64_encode_final(struct base64_encode_ctx *ctx,
 		    uint8_t *dst);