diff --git a/src/eckit/geometry/grid/HEALPix.cc b/src/eckit/geometry/grid/HEALPix.cc
index 2ae2572a9..0a4313eb5 100644
--- a/src/eckit/geometry/grid/HEALPix.cc
+++ b/src/eckit/geometry/grid/HEALPix.cc
@@ -103,7 +103,7 @@ const std::vector<double>& HEALPix::latitudes() const {
 const std::vector<double>& HEALPix::longitudes(size_t i) const {
     const auto Nj    = nj(i);
     const auto step  = 360. / static_cast<double>(Nj);
-    const auto start = static_cast<bool>(i % 2) || i == 0 || i == ni() - 1 ? step / 2. : 0.;
+    const auto start = i < N_ || 3 * N_ - 1 < i || static_cast<bool>((i + N_) % 2) ? step / 2. : 0.;
 
     lons_.reserve(N_ * 4);
     lons_.resize(Nj);