diff --git a/src/image.zig b/src/image.zig
index e031c5a..17a545d 100644
--- a/src/image.zig
+++ b/src/image.zig
@@ -193,7 +193,7 @@ pub const Image = struct {
         sseek(out_file, start);
 
         while (i <= end) : (i += buf.len) {
-            std.debug.warn("i={}, buf.len={}, end={}\n", i, buf.len, end);
+            std.debug.warn("\t\ti={}, buf.len={}, end={}\n", i, buf.len, end);
             sseek(self.sndfile, i);
             sseek(out_file, i);
 
diff --git a/src/lang.zig b/src/lang.zig
index 882cac9..79d38d0 100644
--- a/src/lang.zig
+++ b/src/lang.zig
@@ -7,6 +7,7 @@ pub const ParseError = error{
     UnknownCommand,
     ArgRequired,
     FloatParseFail,
+    ParseFail,
 };
 
 pub const CommandType = enum {
@@ -290,6 +291,7 @@ pub const Lang = struct {
         var splitted_it = std.mem.separate(data, ";");
         try self.fillKeywords();
         var cmds = CommandList.init(self.allocator);
+        var idx: usize = 0;
 
         while (splitted_it.next()) |stmt_orig| {
             var stmt = std.mem.trimRight(u8, stmt_orig, "\n");
@@ -324,9 +326,13 @@ pub const Lang = struct {
             errdefer self.allocator.destroy(cmd_ptr);
 
             cmd_ptr.* = Command{ .command = ctype, .args = args };
-            try self.validateCommand(cmd_ptr);
+            self.validateCommand(cmd_ptr) catch |err| {
+                std.debug.warn("error at line {}: {}\n", idx, err);
+                return ParseError.ParseFail;
+            };
 
             try cmds.append(cmd_ptr);
+            idx += 1;
         }
 
         return cmds;