--- avr-libc-1.7.1.orig/include/avr/pgmspace.h
+++ avr-libc-1.7.1/include/avr/pgmspace.h
@@ -252,7 +252,7 @@
 # define PSTR(s) ((const PROGMEM char *)(s))
 #else  /* !DOXYGEN */
 /* The real thing. */
-# define PSTR(s) (__extension__({static char __c[] PROGMEM = (s); &__c[0];}))
+# define PSTR(s) (__extension__({static const char __c[] PROGMEM = (s); &__c[0];}))
 #endif /* DOXYGEN */
 
 #define __LPM_classic__(addr)   \
--- avr-libc-1.7.1.orig/libc/stdlib/dtostre.c
+++ avr-libc-1.7.1/libc/stdlib/dtostre.c
@@ -37,9 +37,9 @@
 char *
 dtostre (double val, char *sbeg, unsigned char prec, unsigned char flags)
 {
-    __attribute__((progmem)) static char str_nan[2][4] =
+    __attribute__((progmem)) static const char str_nan[2][4] =
 	{"nan", "NAN"};
-    __attribute__((progmem)) static char str_inf[2][sizeof(str_nan[0])] =
+    __attribute__((progmem)) static const char str_inf[2][sizeof(str_nan[0])] =
 	{"inf", "INF"};
     char *d;		/* dst	*/
     char *s;		/* src	*/