diff --git a/src/mir/repres/gauss/reduced/Reduced.cc b/src/mir/repres/gauss/reduced/Reduced.cc
index 2a2470e2b..16ac8f0fd 100644
--- a/src/mir/repres/gauss/reduced/Reduced.cc
+++ b/src/mir/repres/gauss/reduced/Reduced.cc
@@ -345,7 +345,7 @@ std::vector<util::GridBox> Reduced::gridBoxes() const {
                 r.emplace_back(n, w, s, std::min(bbox_.east().value(), lon1.value()));
             }
 
-            ASSERT(lon0 < lon1.normalise(lon0));
+            ASSERT(lon0 <= lon1.normalise(lon0));
         }
     }
 
diff --git a/src/mir/repres/gauss/regular/RegularGG.cc b/src/mir/repres/gauss/regular/RegularGG.cc
index 5f8a6dac9..e49d347a6 100644
--- a/src/mir/repres/gauss/regular/RegularGG.cc
+++ b/src/mir/repres/gauss/regular/RegularGG.cc
@@ -101,7 +101,7 @@ std::vector<util::GridBox> RegularGG::gridBoxes() const {
                            std::max(bbox_.south().value(), latEdges[j + 1]), lonEdges[i + 1]);
         }
 
-        ASSERT(periodic ? lon0 == lon1.normalise(lon0) : lon0 < lon1.normalise(lon0));
+        ASSERT(periodic ? lon0 == lon1.normalise(lon0) : lon0 <= lon1.normalise(lon0));
     }
 
     ASSERT(r.size() == Ni_ * Nj_);
diff --git a/src/mir/repres/latlon/ReducedLL.cc b/src/mir/repres/latlon/ReducedLL.cc
index 47f666c1e..a11f3c13b 100644
--- a/src/mir/repres/latlon/ReducedLL.cc
+++ b/src/mir/repres/latlon/ReducedLL.cc
@@ -325,7 +325,7 @@ std::vector<util::GridBox> ReducedLL::gridBoxes() const {
                 r.emplace_back(util::GridBox(latEdges[j], w, latEdges[j + 1], e));
             }
 
-            ASSERT(lon0 < lon1.normalise(lon0));
+            ASSERT(lon0 <= lon1.normalise(lon0));
         }
     }