diff --git a/vram/VRAMCore_Test.bsv b/vram/VRAMCore_Test.bsv
index 6f0c1df..6923e5e 100644
--- a/vram/VRAMCore_Test.bsv
+++ b/vram/VRAMCore_Test.bsv
@@ -38,8 +38,16 @@ module mkIncrementingValue(ValFn);
 
    function ActionValue#(Bit#(8)) next();
       return (actionvalue
-                 val <= val+1;
-                 return val;
+                 // Cycle through 101 values. 101 is prime, so the
+                 // pattern it generates doesn't align to a power of
+                 // two and should detect any memory mapping errors.
+                 if (val == 100)
+                    val <= 0;
+                 else
+                    val <= val+1;
+                 // Add another number to get all nonzero values, to
+                 // detect writes that don't stick.
+                 return 23+val;
               endactionvalue);
    endfunction