diff --git a/common/AzimuthalIntegrationSettings.cpp b/common/AzimuthalIntegrationSettings.cpp
index de5504c9..54f23bf5 100644
--- a/common/AzimuthalIntegrationSettings.cpp
+++ b/common/AzimuthalIntegrationSettings.cpp
@@ -23,6 +23,10 @@ AzimuthalIntegrationSettings &AzimuthalIntegrationSettings::SolidAngleCorrection
 AzimuthalIntegrationSettings &AzimuthalIntegrationSettings::QRange_recipA(float low, std::optional<float> high) {
     check_finite("Low Q for azimuthal integration", low);
     check_min("Low Q for azimuthal integration", low, minQ_recipA);
+    // The low limit has to leave room for at least one bin below maxQ. This used to follow from the
+    // high limit being mandatory (high <= maxQ and high > low); once "unset" became legal, ResolveHighQ
+    // was left computing std::clamp(q, low + spacing, maxQ) with the lower bound above the upper one.
+    check_max("Low Q for azimuthal integration", low, maxQ_recipA - q_spacing);
     if (high.has_value()) {
         check_finite("High Q for azimuthal integration", *high);
         check_max("High Q for azimuthal integration", *high, maxQ_recipA);