diff --git a/src/fmt.zig b/src/fmt.zig
index aa23d483028dac086f8c0a962b8e225977cd765c..358ebe634a11a0726a6c20fb1bb8d38f7bd68015 100644
--- a/src/fmt.zig
+++ b/src/fmt.zig
@@ -148,7 +148,7 @@ pub fn run(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
         defer gpa.free(formatted);
 
         if (check_flag) {
-            const code: u8 = @intFromBool(mem.eql(u8, formatted, source_code));
+            const code: u8 = @intFromBool(!mem.eql(u8, formatted, source_code));
             process.exit(code);
         }