diff --git a/lib/dictBuilder/zdict.c b/lib/dictBuilder/zdict.c
index 8a38aadeb..874351ebf 100644
--- a/lib/dictBuilder/zdict.c
+++ b/lib/dictBuilder/zdict.c
@@ -505,7 +505,8 @@ static size_t ZDICT_trainBuffer(dictItem* dictList, U32 dictListSize,
     {   size_t pos;
         for (pos=0; pos < bufferSize; pos++)
             reverseSuffix[suffix[pos]] = (U32)pos;
-        /* build file pos */
+        /* note filePos tracks borders between samples.
+           It's not used at this stage, but planned to become useful in a later update */
         filePos[0] = 0;
         for (pos=1; pos<nbFiles; pos++)
             filePos[pos] = (U32)(filePos[pos-1] + fileSizes[pos-1]);