diff --git a/src/qibolab/_core/instruments/qrng.py b/src/qibolab/_core/instruments/qrng.py
index 56a894d20..4b1bc9d14 100644
--- a/src/qibolab/_core/instruments/qrng.py
+++ b/src/qibolab/_core/instruments/qrng.py
@@ -59,11 +59,7 @@ def upscale(samples: npt.NDArray, input_bits=4, output_bits=32) -> npt.NDArray:
 
 
 class QRNG(Instrument):
-    """Driver to sample numbers from a Quantum Random Number Generator (QRNG).
-
-    Note that if we are not connected to a physical QRNG device, this will
-    return pseudo-random generated numbers using ``numpy.random``.
-    """
+    """Driver to sample numbers from a Quantum Random Number Generator (QRNG)."""
 
     address: str
     baudrate: int = 115200
@@ -123,9 +119,6 @@ def extract(self, n: int) -> npt.NDArray:
         Args:
             n: Number of samples to retrieve.
         """
-        if self.port is None:
-            return np.random.randint(0, 2**self.extracted_bits, size=(n,))
-
         samples = self.read(2 * n)
         extracted = self._extractor(samples)
         return extracted
diff --git a/tests/instruments/test_qrng.py b/tests/instruments/test_qrng.py
index b7e5dac09..9ddaaeeae 100644
--- a/tests/instruments/test_qrng.py
+++ b/tests/instruments/test_qrng.py
@@ -10,12 +10,16 @@
 
 
 @pytest.fixture
-def qrng():
+def qrng(mocker):
     qrng = QRNG(address="/dev/ttyACM0")
     try:
         qrng.connect()
     except SerialException:
-        pass
+
+        def extract(n):
+            return np.random.randint(0, 2**qrng.extracted_bits, size=(n,))
+
+        mocker.patch.object(qrng, "extract", side_effect=extract)
     return qrng
 
 
@@ -29,4 +33,4 @@ def test_random_chisquare(qrng):
     expected_frequency = len(data) / nbins
     expected_frequencies = np.full(nbins, expected_frequency)
     _, p_value = chisquare(observed_frequencies, expected_frequencies)
-    assert p_value > 0.05
+    assert p_value > P_VALUE_CUTOFF