diff --git a/scripts/image.lua b/scripts/image.lua
index af67baaf0..b0d08df9c 100644
--- a/scripts/image.lua
+++ b/scripts/image.lua
@@ -12,6 +12,7 @@ local a = Image(32, 64)
 assert(a.width == 32)
 assert(a.height == 64)
 assert(a.colorMode == ColorMode.RGB) -- RGB by default
+assert(a.rowStride == 32*4)
 assert(a:isEmpty())
 assert(a:isPlain(rgba(0, 0, 0, 0)))
 assert(a:isPlain(0))
@@ -21,6 +22,7 @@ do
   assert(b.width == 32)
   assert(b.height == 64)
   assert(b.colorMode == ColorMode.INDEXED)
+  assert(b.rowStride == 32*1)
 
   local c = Image{ width=32, height=64, colorMode=ColorMode.INDEXED }
   assert(c.width == 32)