diff --git a/src/GtkObservables.jl b/src/GtkObservables.jl
index 31fe66f..d4e33ae 100644
--- a/src/GtkObservables.jl
+++ b/src/GtkObservables.jl
@@ -127,11 +127,11 @@ function Graphics.set_coordinates(c::Union{GraphicsContext,Canvas,GtkCanvas}, zr
 end
 function Graphics.set_coordinates(c::Union{Canvas,GtkCanvas}, inds::Tuple{AbstractUnitRange,AbstractUnitRange})
     y, x = inds
-    bb = BoundingBox(first(x), last(x), first(y), last(y))
+    bb = BoundingBox(first(x)-0.5, last(x)+0.5, first(y)-0.5, last(y)+0.5)
     set_coordinates(c, bb)
 end
 function Graphics.BoundingBox(xy::XY)
-    BoundingBox(minimum(xy.x), maximum(xy.x), minimum(xy.y), maximum(xy.y))
+    BoundingBox(minimum(xy.x)-0.5, maximum(xy.x)+0.5, minimum(xy.y)-0.5, maximum(xy.y)+0.5)
 end
 
 function Base.setindex!(zr::Observable{ZoomRegion{T}}, cv::XY{ClosedInterval{S}}) where {T,S}
diff --git a/test/runtests.jl b/test/runtests.jl
index 408e304..af36119 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -344,7 +344,7 @@ end
     @test isa(MouseScroll{UserUnit}(), MouseScroll{UserUnit})
     @test isa(MouseScroll{DeviceUnit}(), MouseScroll{DeviceUnit})
 
-    @test BoundingBox(XY(2..4, -15..15)) === BoundingBox(2, 4, -15, 15)
+    @test BoundingBox(XY(2..4, -15..15)) === BoundingBox(1.5, 4.5, -15.5, 15.5)
 
     c = canvas(208, 207)
     win = GtkWindow(c)
@@ -364,8 +364,8 @@ end
     corner_dev = (DeviceUnit(208), DeviceUnit(207))
     can_test_coords = (get(ENV, "CI", nothing) != "true" || !Sys.islinux()) && can_test_width
     for (coords, corner_usr) in ((BoundingBox(0, 1, 0, 1), (UserUnit(1), UserUnit(1))),
-                                 (ZoomRegion((5:10, 3:5)), (UserUnit(5), UserUnit(10))),
-                                 ((-1:1, 101:110), (UserUnit(110), UserUnit(1))))
+                                 (ZoomRegion((5:10, 3:5)), (UserUnit(5.5), UserUnit(10.5))),
+                                 ((-1:1, 101:110), (UserUnit(110.5), UserUnit(1.5))))
         set_coordinates(c, coords)
         if can_test_coords
             @test GtkObservables.convertunits(DeviceUnit, c, corner_dev...) == corner_dev