diff --git a/src/sudoku.cpp b/src/sudoku.cpp
index 782bfc6..3e6c1bf 100644
--- a/src/sudoku.cpp
+++ b/src/sudoku.cpp
@@ -30,8 +30,8 @@ void Sudoku::Solve(void) {
 
 bool Sudoku::IsBoardSolved(void) {
     int row, column;
-    for (row = 0; row < 9; ++row) {
-        for (column = 0; column < 9; ++column) {
+    for (row = 0; row < 9; row += 3) {
+        for (column = 0; column < 9; column += 3) {
             if (!GetUnusedRow(row).empty()) { return false; }
             if (!GetUnusedColumn(column).empty()) { return false; }
             if (!GetUnusedSubgrid(row, column).empty()) { return false; }