PROGMEM is required...
#include <avr/pgmspace.h>
void setup() {
Serial.begin(115200);
Serial.write("Here we go...\n");
static prog_uint32_t TESTCONSTANT PROGMEM = 4000000;
Serial.write("TESTCONSTANT=");
Serial.println(pgm_read_dword_near(&TESTCONSTANT));
}
void loop() {
}