diff --git a/strobe_rng_init.c b/strobe_rng_init.c
index f4b0b71..3576cf2 100644
--- a/strobe_rng_init.c
+++ b/strobe_rng_init.c
@@ -33,18 +33,14 @@
 
 #include <utilities.h>
 
+#include <unistd.h>
+
 #define nitems(x)	(sizeof(x) / sizeof *(x))
 #define DEFINE_RNG_SAVE	1
 #if DEFINE_RNG_SAVE
 const rng_word_t rng_save[roundup(32, sizeof(rng_word_t)) / sizeof(rng_word_t)] __attribute__ ((section (".eeprom")));
 #endif
 
-/*
- * Note: This is the end of allocated SRAM, aka, the begining of
- * uninitalized SRAM.
- */
-extern uint8_t end;
-
 void
 strobe_rng_init(void)
 {
@@ -58,8 +54,10 @@ strobe_rng_init(void)
 	/*
 	 * On first boot, SRAM is uninitialized and randomness from
 	 * it is used.
+	 *
+	 * Note: This depends upon sbrk pointing to uinitalized SRAM.
 	 */
-	strobe_seed_prng(&end, 2*1024);
+	strobe_seed_prng(sbrk(0), 2*1024);
 
 }