diff --git a/lib/hts221/hts221/device.py b/lib/hts221/hts221/device.py
index 6a899080..0eb35213 100644
--- a/lib/hts221/hts221/device.py
+++ b/lib/hts221/hts221/device.py
@@ -110,6 +110,12 @@ def trigger_one_shot(self):
     def _ensure_data(self):
         if self._is_power_down() or self._is_one_shot_mode():
             self.trigger_one_shot()
+            ready_mask = HTS221_STATUS_T_DA | HTS221_STATUS_H_DA
+            for _ in range(50):
+                if (self._read_reg(HTS221_STATUS_REG) & ready_mask) == ready_mask:
+                    return
+                sleep_ms(2)
+            raise OSError("HTS221 data ready timeout")
 
     # calculate Temperature
     def temperature(self):
diff --git a/tests/scenarios/hts221.yaml b/tests/scenarios/hts221.yaml
index 66f893cd..d252e3c5 100644
--- a/tests/scenarios/hts221.yaml
+++ b/tests/scenarios/hts221.yaml
@@ -136,6 +136,20 @@ tests:
     expect_true: true
     mode: [mock]
 
+  - name: "Timeout raises OSError when data never ready"
+    action: script
+    script: |
+      dev.poweroff()
+      i2c._registers[0x27] = bytes([0x00])
+      try:
+          dev.temperature()
+          result = False
+      except OSError:
+          result = True
+      i2c._registers[0x27] = bytes([0x03])
+    expect_true: true
+    mode: [mock]
+
   - name: "Auto-trigger after poweroff"
     action: hardware_script
     script: |