diff --git a/news/x2xcorrphase-public.rst b/news/x2xcorrphase-public.rst
new file mode 100644
index 0000000..45ccd5d
--- /dev/null
+++ b/news/x2xcorrphase-public.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* Expose PowderPatternDiffraction.X2XCorrPhase
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>
diff --git a/src/extensions/powderpatterndiffraction_ext.cpp b/src/extensions/powderpatterndiffraction_ext.cpp
index def3afa..839c925 100644
--- a/src/extensions/powderpatterndiffraction_ext.cpp
+++ b/src/extensions/powderpatterndiffraction_ext.cpp
@@ -90,6 +90,7 @@ void wrap_powderpatterndiffraction()
                 &PowderPatternDiffraction::GetNbReflBelowMaxSinThetaOvLambda)
         .def("GetFhklObsSq", &PowderPatternDiffraction::GetFhklObsSq,
                 return_value_policy<copy_const_reference>())
+        .def("X2XCorrPhase", &PowderPatternDiffraction::X2XCorrPhase)
         ;
 
 }
diff --git a/tests/test_powderpattern.py b/tests/test_powderpattern.py
index b1d43dc..a5420a1 100644
--- a/tests/test_powderpattern.py
+++ b/tests/test_powderpattern.py
@@ -364,7 +364,35 @@ class TestPowderPatternBackground(unittest.TestCase):
 
 
 class TestPowderPatternDiffraction(unittest.TestCase):
-    pass
+    def test_X2XCorrPhase_flat_detector_displacement(self):
+        pp = PowderPattern()
+        pp.SetWavelength(1.54056)
+        pp.SetPowderPatternPar(np.deg2rad(5), np.deg2rad(0.1), 851)
+        crystal = makeCrystal(*makeScatterer())
+        pdiff = pp.AddPowderPatternDiffraction(crystal)
+
+        x = np.deg2rad(30)
+        self.assertAlmostEqual(pdiff.X2XCorrPhase(x), x)
+
+        phase_ratio = 1e-4
+        pdiff.GetPar("2ThetaFlatDetDispRatioPhase").SetValue(phase_ratio)
+        expected = x + np.arctan(
+            phase_ratio
+            * np.sin(2 * x)
+            / (2 - 2 * phase_ratio * np.sin(x) ** 2)
+        )
+        self.assertAlmostEqual(pdiff.X2XCorrPhase(x), expected)
+
+        pattern_ratio = 2e-4
+        pp.GetPar("2ThetaFlatDetDispRatio").SetValue(pattern_ratio)
+        total_ratio = phase_ratio + pattern_ratio
+        expected = x + np.arctan(
+            total_ratio
+            * np.sin(2 * x)
+            / (2 - 2 * total_ratio * np.sin(x) ** 2)
+        )
+        self.assertAlmostEqual(pdiff.X2XCorrPhase(x), expected)
+
     # def test___init__(self):  assert False
     # def test_ExtractLeBail(self):  assert False
     # def test_GetExtractionMode(self):  assert False