diff --git a/common/AzimuthalIntegrationProfile.cpp b/common/AzimuthalIntegrationProfile.cpp
index d4794e38..165bfe27 100644
--- a/common/AzimuthalIntegrationProfile.cpp
+++ b/common/AzimuthalIntegrationProfile.cpp
@@ -44,6 +44,7 @@ void AzimuthalIntegrationProfile::Clear(const AzimuthalIntegrationMapping &mappi
     azim_bins = mapping.GetAzimuthalBinCount();
 
     sum = std::vector<float>(mapping.GetBinNumber(), 0);
+    sum2 = std::vector<float>(mapping.GetBinNumber(), 0);
     count = std::vector<uint64_t>(mapping.GetBinNumber(), 0);
 }
 
diff --git a/tests/AzimuthalIntegrationTest.cpp b/tests/AzimuthalIntegrationTest.cpp
index ed49b531..b455920a 100644
--- a/tests/AzimuthalIntegrationTest.cpp
+++ b/tests/AzimuthalIntegrationTest.cpp
@@ -256,6 +256,69 @@ TEST_CASE("AzimuthalIntegrationProfile_GetStd","[AzimuthalIntegration]") {
     CHECK(ret_count[3] == 0);
 }
 
+TEST_CASE("AzimuthalIntegrationProfile_GetStd_AfterClear","[AzimuthalIntegration]") {
+    DiffractionExperiment x(DetJF4M());
+    x.DetectorDistance_mm(50).BeamX_pxl(1000).BeamY_pxl(1000);
+    x.QSpacingForAzimInt_recipA(0.1).QRangeForAzimInt_recipA(0.1, 4);
+
+    PixelMask pixel_mask(x);
+    AzimuthalIntegrationMapping mapping(x, pixel_mask);
+
+    AzimuthalIntegrationProfile profile(mapping);
+
+    std::vector<float> sum(mapping.GetBinNumber()), sum2(mapping.GetBinNumber());
+    std::vector<uint32_t> count(mapping.GetBinNumber());
+
+    sum[0] = 2 + 3 + 4 + 5;
+    sum2[0] = 4 + 9 + 16 + 25;
+    count[0] = 4;
+
+    // The same frame twice, with a Clear() in between: a profile is reused for every image of a
+    // dataset, so the second image has to give exactly the first one's standard deviation.
+    profile.Add(sum, sum2, count);
+    const auto first = profile.GetStd();
+
+    profile.Clear(mapping);
+    profile.Add(sum, sum2, count);
+    const auto second = profile.GetStd();
+
+    CHECK(first[0] == Catch::Approx(std::sqrt(5.0 / 3.0)));
+    CHECK(second[0] == Catch::Approx(first[0]));
+}
+
+TEST_CASE("AzimuthalIntegrationProfile_ClearToLargerMapping","[AzimuthalIntegration]") {
+    DiffractionExperiment x(DetJF4M());
+    x.DetectorDistance_mm(50).BeamX_pxl(1000).BeamY_pxl(1000);
+    x.QSpacingForAzimInt_recipA(0.1).QRangeForAzimInt_recipA(0.1, 4);
+
+    PixelMask pixel_mask(x);
+    AzimuthalIntegrationMapping small(x, pixel_mask);
+
+    // A wider q range - the viewer re-uses one profile across datasets, so every vector Clear()
+    // touches has to end up the size the new mapping asks for.
+    x.QRangeForAzimInt_recipA(0.1, 9);
+    AzimuthalIntegrationMapping large(x, pixel_mask);
+    REQUIRE(large.GetBinNumber() > small.GetBinNumber());
+
+    AzimuthalIntegrationProfile profile(small);
+    profile.Clear(large);
+
+    std::vector<float> sum(large.GetBinNumber()), sum2(large.GetBinNumber());
+    std::vector<uint32_t> count(large.GetBinNumber());
+
+    // A bin that exists only in the wider mapping.
+    const auto bin = small.GetBinNumber();
+    sum[bin] = 2 + 3 + 4 + 5;
+    sum2[bin] = 4 + 9 + 16 + 25;
+    count[bin] = 4;
+
+    profile.Add(sum, sum2, count);
+
+    const auto stddev = profile.GetStd();
+    REQUIRE(stddev.size() == large.GetBinNumber());
+    CHECK(stddev[bin] == Catch::Approx(std::sqrt(5.0 / 3.0)));
+}
+
 TEST_CASE("AzimuthalIntegrationProfile_operatorAdd","[AzimuthalIntegration]") {
     DiffractionExperiment x(DetJF4M());
     x.DetectorDistance_mm(50).BeamX_pxl(1000).BeamY_pxl(1000);