diff --git a/_FiveSql2/src/TSqlAgg.prg b/_FiveSql2/src/TSqlAgg.prg
index 4b2399f..d6f2992 100644
--- a/_FiveSql2/src/TSqlAgg.prg
+++ b/_FiveSql2/src/TSqlAgg.prg
@@ -404,6 +404,13 @@ METHOD ComputeAgg( xE, aGR, aFN ) CLASS TSqlAgg
    ENDIF
 
    nCol := ::FindColIdx2( cArgName, aFN )
+   /* Also try the QUALIFIED name from the AST (e.g. "o.amount") since
+    * the Go SqlHashJoin fast path preserves qualifier prefixes in
+    * aFieldNames for JOIN disambiguation. SqlExprName strips them
+    * but the hidden column might be stored with the full qualified form. */
+   IF nCol == 0 .AND. xArg[ 1 ] == ND_COL .AND. xArg[ 2 ] != cArgName
+      nCol := ::FindColIdx2( Upper( xArg[ 2 ] ), aFN )
+   ENDIF
    IF nCol == 0 .AND. xArg[ 1 ] == ND_COL
       IF cFunc == "COUNT"
          RETURN Len( aGR )