diff --git a/src/include/stir/DetectorCoordinateMap.h b/src/include/stir/DetectorCoordinateMap.h
index 5e427a40c..1278abc1c 100644
--- a/src/include/stir/DetectorCoordinateMap.h
+++ b/src/include/stir/DetectorCoordinateMap.h
@@ -123,6 +123,8 @@ class DetectorCoordinateMap
   explicit DetectorCoordinateMap(double sigma = 0.0)
       : sigma(sigma)
   {
+    if (sigma == 0.0)
+      return;
 #  ifdef STIR_OPENMP
     generators.resize(omp_get_max_threads());
     distributions.resize(omp_get_max_threads());