diff --git a/Graph Views/XRGDiskView.m b/Graph Views/XRGDiskView.m
index e8d63b1..ea593fb 100644
--- a/Graph Views/XRGDiskView.m	
+++ b/Graph Views/XRGDiskView.m	
@@ -39,7 +39,7 @@ @implementation XRGDiskView
 
 - (void)awakeFromNib {    
     currentIndex = 0;
-    maxVal       = 0;
+    maxVal       = 1;
 	fastMax      = 1024 * 1024;
               
     parentWindow = (XRGGraphWindow *)[self window];
@@ -456,6 +456,8 @@ - (void)clearData:(NSEvent *)theEvent {
         readValues[i] = 0;
         writeValues[i] = 0;
     }
+
+    maxVal = 1;
 }
 
 - (BOOL)acceptsFirstMouse:(NSEvent *)theEvent {