diff --git a/debian/changelog b/debian/changelog
index d26a5aaf79c6..170fd092d927 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -2,6 +2,8 @@
   * Upgraded Django version to version 3.2.21 with a security fix
 
   [Michele Simionato]
+  * In case of a well known IndexError in disaggregation calculations, solved in
+    newer versions of the engine, a helpful message is printed
   * Backported fix on sanity check for avg_losses and aggrisk
   * Backported fix to `avg_gmf`
   * Backported a fix to `oq reaggregate`
diff --git a/openquake/calculators/disaggregation.py b/openquake/calculators/disaggregation.py
index c8ad55a669a2..c658786fde35 100644
--- a/openquake/calculators/disaggregation.py
+++ b/openquake/calculators/disaggregation.py
@@ -59,6 +59,8 @@ def _collapse_res(rdic):
 def _matrix(matrices, num_trts, num_mag_bins):
     # convert a dict trti, magi -> matrix into a single matrix
     trti, magi = next(iter(matrices))
+    if trti >= num_trts:
+        raise IndexError('please upgrade to engine >= 3.17')
     mat = numpy.zeros((num_trts, num_mag_bins) + matrices[trti, magi].shape)
     for trti, magi in matrices:
         mat[trti, magi] = matrices[trti, magi]