diff --git a/src/library/module.cpp b/src/library/module.cpp
index baabee9f4c25..f03bd7befba9 100644
--- a/src/library/module.cpp
+++ b/src/library/module.cpp
@@ -52,7 +52,8 @@ struct olean_header {
     // 1 byte: version, incremented on structural changes to header
     uint8_t version = 2;
     // 1 byte of flags:
-    // - whether persisted bignums use GMP or Lean-native encoding
+    // * bit 0: whether persisted bignums use GMP or Lean-native encoding
+    // * bit 1-7: reserved
     uint8_t flags =
 #ifdef LEAN_USE_GMP
         0b1;
@@ -60,7 +61,7 @@ struct olean_header {
         0b0;
 #endif
     // 33 bytes: Lean version string, padded with '\0' to the right
-    // e.g. "4.12.0-nightly-2024-10-18"
+    // e.g. "4.12.0-nightly-2024-10-18". May not be null-terminated.
     char lean_version[33];
     // 81b008650766442a0dfa9faa796e4588c9d7d3a1
     // 40 bytes: build githash, padded with `\0` to the right