diff --git a/src/samplesrc/hgrtest.pla b/src/samplesrc/hgrtest.pla
index d8a9b6b..168365c 100644
--- a/src/samplesrc/hgrtest.pla
+++ b/src/samplesrc/hgrtest.pla
@@ -21,10 +21,10 @@ def testline#0
 
   setlinespans(@hgrHlin, @hgrVlin)
   hgrColor(7)
-  for i = 0 to 191 step 16
+  for i = 0 to 191 step 8
     linespans(0, i, 279, 191 - i)
   next
-  for i = 0 to 279 step 14
+  for i = 0 to 279 step 9
     linespans(i, 0, 279 - i, 191)
   next
 end