diff --git a/shared/include/HDMapping/PoseInterpolation.h b/shared/include/HDMapping/PoseInterpolation.h
index 4718c150..86ee5f0d 100644
--- a/shared/include/HDMapping/PoseInterpolation.h
+++ b/shared/include/HDMapping/PoseInterpolation.h
@@ -27,6 +27,11 @@ inline Eigen::Matrix4d getInterpolatedPose(const std::map<double, Eigen::Matrix4
     {
         return ret;
     }
+    // query_time is past the last pose; end() must be caught before it_lower is dereferenced
+    if (it_lower == trajectory.end())
+    {
+        return ret;
+    }
     if (it_lower->first > query_time)
     {
         it_lower = std::prev(it_lower);
@@ -35,10 +40,6 @@ inline Eigen::Matrix4d getInterpolatedPose(const std::map<double, Eigen::Matrix4
     {
         return ret;
     }
-    if (it_lower == trajectory.end())
-    {
-        return ret;
-    }
 
     constexpr double MaxInterpolationS = 0.1;
     double t1 = it_lower->first;
diff --git a/shared/tests/CMakeLists.txt b/shared/tests/CMakeLists.txt
index 82be362f..ed7d3bd4 100644
--- a/shared/tests/CMakeLists.txt
+++ b/shared/tests/CMakeLists.txt
@@ -22,5 +22,11 @@ if (MSVC)
     target_compile_definitions(hdmapping_shared_tests PRIVATE _USE_MATH_DEFINES)
 endif()
 
+# Build in libstdc++ debug mode so iterator misuse (e.g. dereferencing end())
+# fails the test run instead of passing by luck. Safe because the code under
+# test is header-only and no other C++ library is linked in; other standard
+# libraries ignore the macro.
+target_compile_definitions(hdmapping_shared_tests PRIVATE _GLIBCXX_DEBUG)
+
 include(CTest)
 add_test(NAME hdmapping_shared_tests COMMAND hdmapping_shared_tests)
diff --git a/shared/tests/test_pose_interpolation.cpp b/shared/tests/test_pose_interpolation.cpp
index ac357c44..e95c0e2e 100644
--- a/shared/tests/test_pose_interpolation.cpp
+++ b/shared/tests/test_pose_interpolation.cpp
@@ -39,6 +39,19 @@ TEST_CASE("getInterpolatedPose: query before the first timestamp returns a zero
     CHECK(isZeroMatrix(getInterpolatedPose(traj, -100.0)));
 }
 
+TEST_CASE("getInterpolatedPose: query after the last timestamp returns a zero matrix")
+{
+    // lower_bound() returns end() here, which must not be dereferenced --
+    // the _GLIBCXX_DEBUG build of this test (see CMakeLists.txt) aborts if it is.
+    std::map<double, Eigen::Matrix4d> traj{
+        { 1.0, makePose(0, 0, 0) },
+        { 2.0, makePose(10, 0, 0) },
+        { 3.0, makePose(20, 0, 0) },
+    };
+    CHECK(isZeroMatrix(getInterpolatedPose(traj, 3.5)));
+    CHECK(isZeroMatrix(getInterpolatedPose(traj, 100.0)));
+}
+
 TEST_CASE("getInterpolatedPose: exact match at an interior timestamp returns that exact pose")
 {
     // Interior = not the very first key -- see the "first segment" case below