diff --git a/apps/graph/test/ranges.cpp b/apps/graph/test/ranges.cpp
index 5056fd343..a2f5b8edf 100644
--- a/apps/graph/test/ranges.cpp
+++ b/apps/graph/test/ranges.cpp
@@ -71,7 +71,7 @@ QUIZ_CASE(graph_ranges_single_function) {
 
   assert_best_cartesian_range_is("0", -10, 10, -5.81249952, 4.81249952);
   assert_best_cartesian_range_is("1", -10, 10, -4.81249952, 5.81249952);
-  assert_best_cartesian_range_is("-100", -10, 10, -105.662506, -95.0375061);
+  assert_best_cartesian_range_is("-100", -10, 10, -105.8125, -95.1875);
   assert_best_cartesian_range_is("0.01", -10, 10, -5.81249952, 4.81249952);
 
   assert_best_cartesian_range_is("x", -10, 10, -5.66249943, 4.96249962);
diff --git a/poincare/src/zoom.cpp b/poincare/src/zoom.cpp
index b999a4d17..ac9eb6390 100644
--- a/poincare/src/zoom.cpp
+++ b/poincare/src/zoom.cpp
@@ -317,7 +317,7 @@ void Zoom::RangeWithRatioForDisplay(ValueAtAbscissa evaluation, float yxRatio, f
    * X axis. Conversely, very flat functions may only take a small portion of
    * the Y range. In those cases, the ratio is not suitable. */
   if (bestBreadth < minimalXCoverage * sampleSize
-   || sample[bestIndex + bestBreadth] - sample[bestIndex] < minimalYCoverage * yRange) {
+   || sample[bestIndex + bestBreadth - 1] - sample[bestIndex] < minimalYCoverage * yRange) {
     *xMin = NAN;
     *xMax = NAN;
     *yMin = NAN;