diff --git a/main/system.c b/main/system.c
index 1358def36..0c4abe811 100644
--- a/main/system.c
+++ b/main/system.c
@@ -269,10 +269,10 @@ static double _calculate_network_difficulty(uint32_t nBits)
 
 static void _check_for_best_diff(SystemModule * module, double diff, uint32_t nbits)
 {
-    if (diff <= module->best_nonce_diff) {
+    if ((uint64_t) diff <= module->best_nonce_diff) {
         return;
     }
-    module->best_nonce_diff = diff;
+    module->best_nonce_diff = (uint64_t) diff;
 
     nvs_config_set_u64(NVS_CONFIG_BEST_DIFF, module->best_nonce_diff);
 
diff --git a/main/system.h b/main/system.h
index c7ca43fe1..13d4ae252 100644
--- a/main/system.h
+++ b/main/system.h
@@ -21,7 +21,7 @@ typedef struct
     uint16_t shares_rejected;
     int screen_page;
     char oled_buf[20];
-    uint32_t best_nonce_diff;
+    uint64_t best_nonce_diff;
     char best_diff_string[DIFF_STRING_SIZE];
     bool FOUND_BLOCK;
     bool startup_done;