diff --git a/glcdfont.c b/glcdfont.c
index abc3631..ebf7472 100644
--- a/glcdfont.c
+++ b/glcdfont.c
@@ -6,7 +6,7 @@
 
 // standard ascii 5x7 font
 
-static unsigned char  font[] PROGMEM = {
+static const unsigned char  font[] PROGMEM = {
         0x00, 0x00, 0x00, 0x00, 0x00,   
 	0x3E, 0x5B, 0x4F, 0x5B, 0x3E, 	
 	0x3E, 0x6B, 0x4F, 0x6B, 0x3E,