diff --git a/freqtrade/optimize/space/decimalspace.py b/freqtrade/optimize/space/decimalspace.py
index bcf74feb8..40a8115f9 100644
--- a/freqtrade/optimize/space/decimalspace.py
+++ b/freqtrade/optimize/space/decimalspace.py
@@ -8,7 +8,7 @@ class SKDecimal(FloatDistribution):
         high: float,
         *,
         step: float | None = None,
-        decimals: int = 3,
+        decimals: int | None = None,
         name=None,
     ):
         """
@@ -22,6 +22,8 @@ class SKDecimal(FloatDistribution):
         """
         if decimals is not None and step is not None:
             raise ValueError("You can only set one of decimals or step")
+        if decimals is None and step is None:
+            raise ValueError("You must set one of decimals or step")
         # Convert decimals to step
         self.step = step or 1 / 10**decimals
         self.name = name
diff --git a/tests/optimize/test_hyperopt.py b/tests/optimize/test_hyperopt.py
index 0e3d24511..c22323bdf 100644
--- a/tests/optimize/test_hyperopt.py
+++ b/tests/optimize/test_hyperopt.py
@@ -1197,6 +1197,9 @@ def test_SKDecimal():
     with pytest.raises(ValueError):
         SKDecimal(1, 2, step=5, decimals=0.2)
 
+    with pytest.raises(ValueError):
+        SKDecimal(1, 2, step=None, decimals=None)
+
     s = SKDecimal(1, 2, step=0.1, decimals=None)
     assert s.step == 0.1
     assert s._contains(1.1)