diff --git a/freqtrade/optimize/optimize_reports/optimize_reports.py b/freqtrade/optimize/optimize_reports/optimize_reports.py
index a5d38b850..15d25a19c 100644
--- a/freqtrade/optimize/optimize_reports/optimize_reports.py
+++ b/freqtrade/optimize/optimize_reports/optimize_reports.py
@@ -340,7 +340,7 @@ def generate_strategy_comparison(bt_stats: dict) -> list[dict]:
 
 def _get_resample_from_period(period: str) -> str:
     if period == "day":
-        return "1d"
+        return "1D"
     if period == "week":
         # Weekly defaulting to Monday.
         return "1W-MON"
@@ -530,8 +530,8 @@ def generate_daily_stats(results: DataFrame) -> dict[str, Any]:
             "losing_days": 0,
             "daily_profit_list": [],
         }
-    daily_profit_rel = results.resample("1d", on="close_date")["profit_ratio"].sum()
-    daily_profit = results.resample("1d", on="close_date")["profit_abs"].sum().round(10)
+    daily_profit_rel = results.resample("1D", on="close_date")["profit_ratio"].sum()
+    daily_profit = results.resample("1D", on="close_date")["profit_abs"].sum().round(10)
     worst_rel = min(daily_profit_rel)
     best_rel = max(daily_profit_rel)
     worst = min(daily_profit)
diff --git a/tests/optimize/test_optimize_reports.py b/tests/optimize/test_optimize_reports.py
index c54dea689..fcf5abffd 100644
--- a/tests/optimize/test_optimize_reports.py
+++ b/tests/optimize/test_optimize_reports.py
@@ -713,7 +713,7 @@ def test_generate_periodic_breakdown_stats(testdatadir):
 
 
 def test__get_resample_from_period():
-    assert _get_resample_from_period("day") == "1d"
+    assert _get_resample_from_period("day") == "1D"
     assert _get_resample_from_period("week") == "1W-MON"
     assert _get_resample_from_period("month") == "1ME"
     assert _get_resample_from_period("weekday") == "weekday"