diff --git a/firmware/lib/cgptlib/cgptlib.c b/firmware/lib/cgptlib/cgptlib.c
index 2dcb46d..e708b7b 100644
--- a/firmware/lib/cgptlib/cgptlib.c
+++ b/firmware/lib/cgptlib/cgptlib.c
@@ -44,7 +44,7 @@
       e = entries + i;
       if (!IsKernelEntry(e))
         continue;
-      VBDEBUG(("GptNextKernelEntry looking at same prio partition %d\n", i));
+      VBDEBUG(("GptNextKernelEntry looking at same prio partition %d\n", i+1));
       VBDEBUG(("GptNextKernelEntry s%d t%d p%d\n",
                GetEntrySuccessful(e), GetEntryTries(e), GetEntryPriority(e)));
       if (!(GetEntrySuccessful(e) || GetEntryTries(e)))
@@ -65,7 +65,7 @@
     int current_prio = GetEntryPriority(e);
     if (!IsKernelEntry(e))
       continue;
-    VBDEBUG(("GptNextKernelEntry looking at new prio partition %d\n", i));
+    VBDEBUG(("GptNextKernelEntry looking at new prio partition %d\n", i+1));
     VBDEBUG(("GptNextKernelEntry s%d t%d p%d\n",
              GetEntrySuccessful(e), GetEntryTries(e), GetEntryPriority(e)));
     if (!(GetEntrySuccessful(e) || GetEntryTries(e)))
diff --git a/firmware/lib/cgptlib/include/cgptlib.h b/firmware/lib/cgptlib/include/cgptlib.h
index 4eadc81..451ecf0 100644
--- a/firmware/lib/cgptlib/include/cgptlib.h
+++ b/firmware/lib/cgptlib/include/cgptlib.h
@@ -61,7 +61,10 @@
                                   * 0x04 = table1
                                   * 0x08 = table2  */
   int current_kernel; /* the current chromeos kernel index in partition table.
-                       * -1 means not found on drive. */
+                       * -1 means not found on drive. Note that GPT partition
+                       * numbers are traditionally 1-based, but we're using
+                       * a zero-based index here.
+                       */
 
   /* Internal variables */
   uint32_t valid_headers, valid_entries;