diff --git a/src/quant_engine/portfolio_construction.py b/src/quant_engine/portfolio_construction.py
index 90e2d7d..88487de 100644
--- a/src/quant_engine/portfolio_construction.py
+++ b/src/quant_engine/portfolio_construction.py
@@ -81,6 +81,8 @@ def scores_to_weight_table(
         raise TypeError(f"scores must be a pandas DataFrame, got {type(scores).__name__}")
     _validate_top_k(top_k)
     _validate_gross_exposure(gross_exposure)
+    if not scores.index.is_unique:
+        raise ValueError("scores must contain unique rebalance dates")
     if not scores.columns.is_unique:
         raise ValueError("scores must contain unique asset labels")
     if not all(is_numeric_dtype(dtype) for dtype in scores.dtypes):