diff --git a/main.c b/main.c
index 655fe50..d35e1de 100644
--- a/main.c
+++ b/main.c
@@ -68,7 +68,8 @@ static update_res_t update(state_t *state, int *x_out, int *y_out)
 
 	for (int y = 0; y < HEIGHT; ++y) {
 		for (int x = 0; x < WIDTH; ++x) {
-			if (state->field[x][y] == UNKNOWN || state->field[x][y] == MINE)
+			if (state->field[x][y] == UNKNOWN || state->field[x][y] == MINE
+			    || state->field[x][y] == SAFE)
 				continue;
 
 			const int mines = countadj(state->field, x, y, MINE);
diff --git a/puzz.c b/puzz.c
index e797830..b4d0a32 100644
--- a/puzz.c
+++ b/puzz.c
@@ -106,8 +106,18 @@ status_t check(puzz_t puzz)
 {
 	for (int y = 0; y < HEIGHT; ++y) {
 		for (int x = 0; x < WIDTH; ++x) {
-			if (puzz[x][y] != UNKNOWN && puzz[x][y] != soln[x][y])
-				return INCORRECT;
+			switch (puzz[x][y]) {
+			case UNKNOWN:
+				continue;
+			case SAFE:
+				if (soln[x][y] == MINE)
+					return INCORRECT;
+				break;
+			default:
+				if (puzz[x][y] != soln[x][y])
+					return INCORRECT;
+				break;
+			}
 		}
 	}
 	return OK;
diff --git a/puzz.h b/puzz.h
index 34e66ce..d819c05 100644
--- a/puzz.h
+++ b/puzz.h
@@ -12,7 +12,7 @@
 
 #include <stdint.h>
 
-enum { MINE = 0xff, UNKNOWN = 0xfe };
+enum { MINE = 0xff, UNKNOWN = 0xfe, SAFE = 0xfd };
 
 typedef uint8_t puzz_t[WIDTH][HEIGHT];
 typedef enum { DEAD, OK, INCORRECT } status_t;