diff --git a/talipp/indicators/IBS.py b/talipp/indicators/IBS.py
index 24cd330..0894c7e 100644
--- a/talipp/indicators/IBS.py
+++ b/talipp/indicators/IBS.py
@@ -35,4 +35,4 @@ def _calculate_new_value(self) -> Any:
             return None
 
         candle: OHLCV = self.input_values[-1]
-        return (candle.close - candle.low) / (candle.high - candle.low)
+        return None if candle.high == candle.low else (candle.close - candle.low) / (candle.high - candle.low)
diff --git a/talipp/indicators/UO.py b/talipp/indicators/UO.py
index c22bc57..5816f3a 100644
--- a/talipp/indicators/UO.py
+++ b/talipp/indicators/UO.py
@@ -58,8 +58,15 @@ def _calculate_new_value(self) -> Any:
         if not has_valid_values(self.buy_press, self.slow_period):
             return None
 
-        avg_fast = sum(self.buy_press[-self.fast_period:]) / float(sum(self.true_range[-self.fast_period:]))
-        avg_mid = sum(self.buy_press[-self.mid_period:]) / float(sum(self.true_range[-self.mid_period:]))
-        avg_slow = sum(self.buy_press[-self.slow_period:]) / float(sum(self.true_range[-self.slow_period:]))
+        fast_sum = sum(self.true_range[-self.fast_period:])
+        mid_sum = sum(self.true_range[-self.mid_period:])
+        slow_sum = sum(self.true_range[-self.slow_period:])
+
+        if fast_sum == 0 or mid_sum == 0 or slow_sum == 0:
+            return None
+
+        avg_fast = sum(self.buy_press[-self.fast_period:]) / float(fast_sum)
+        avg_mid = sum(self.buy_press[-self.mid_period:]) / float(mid_sum)
+        avg_slow = sum(self.buy_press[-self.slow_period:]) / float(slow_sum)
 
         return 100.0 * (4.0 * avg_fast + 2.0 * avg_mid + avg_slow) / 7.0