diff --git a/testpar/testphdf5.h b/testpar/testphdf5.h
index 4cf27c0040..076bf5ae4b 100644
--- a/testpar/testphdf5.h
+++ b/testpar/testphdf5.h
@@ -48,7 +48,7 @@
 
 /* Constants definitions */
 #define DIM0		600 	/* Default dataset sizes. */
-#define DIM1		800	/* Values are from a monitor pixel sizes */
+#define DIM1		1200	/* Values are from a monitor pixel sizes */
 #define RANK		2
 #define DATASETNAME1	"Data1"
 #define DATASETNAME2	"Data2"