diff --git a/internal/buildfile/reader_test.go b/internal/buildfile/reader_test.go
index 6654b92..6a18a9b 100644
--- a/internal/buildfile/reader_test.go
+++ b/internal/buildfile/reader_test.go
@@ -15,7 +15,7 @@ func TestNullContext(t *testing.T) {
 }
 func TestIgnoreCommentsAndEmptyLines(t *testing.T) {
 	ctx, _ := instruction.CreateContext("apt-get", "")
-	buffer := bytes.NewBufferString("[ some comment ]\n\n  \t  \n\t  \t\n[ other comment after empty lines ]")
+	buffer := bytes.NewBufferString("# some comment\n;other comment\n  \t  \n\t  \t\n; other comment after empty lines")
 
 	r, err := NewReader(ctx, buffer)
 	if err != nil {
@@ -33,24 +33,24 @@ func TestInstructionSyntax(t *testing.T) {
 		Line int
 		Err  error
 	}{
-		{"install args\ndelete args\n", 0, nil},
-		{" install args\ndelete args\n", 0, nil},
-		{"\tinstall args\ndelete args\n", 0, nil},
-		{" \t install args\ndelete args\n", 0, nil},
-		{" \t install args\ndelete args\n", 0, nil},
+		{"[pre]\ninstall args\ndelete args\n", 1, nil},
+		{"[pre]\n install args\ndelete args\n", 1, nil},
+		{"[pre]\n\tinstall args\ndelete args\n", 1, nil},
+		{"[pre]\n \t install args\ndelete args\n", 1, nil},
+		{"[pre]\n \t install args\ndelete args\n", 1, nil},
 
-		{"cmd args\ncmd args\n", 1, instruction.ErrUnknownInstruction},
-		{"install args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
-		{" cmd args\ncmd args\n", 1, instruction.ErrUnknownInstruction},
-		{"\tcmd args\ncmd args\n", 1, instruction.ErrUnknownInstruction},
-		{" \t cmd args\ncmd args\n", 1, instruction.ErrUnknownInstruction},
-		{" \t cmd args\ncmd args\n", 1, instruction.ErrUnknownInstruction},
+		{"[pre]\ncmd args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
+		{"[pre]\ninstall args\ncmd args\n", 3, instruction.ErrUnknownInstruction},
+		{"[pre]\n cmd args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
+		{"[pre]\n\tcmd args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
+		{"[pre]\n \t cmd args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
+		{"[pre]\n \t cmd args\ncmd args\n", 2, instruction.ErrUnknownInstruction},
 
-		{"cmd args\ncmd\n", 1, instruction.ErrUnknownInstruction},
-		{"install\ncmd args\n", 1, instruction.ErrInvalidSyntax},
+		{"[pre]\ncmd args\ncmd\n", 2, instruction.ErrUnknownInstruction},
+		{"[pre]\ninstall\ncmd args\n", 2, instruction.ErrInvalidSyntax},
 
-		{"install args\n cmd args\n", 2, instruction.ErrUnknownInstruction},
-		{"install args\ncmd\n", 2, instruction.ErrInvalidSyntax},
+		{"[pre]\ninstall args\n cmd args\n", 3, instruction.ErrUnknownInstruction},
+		{"[pre]\ninstall args\ncmd\n", 3, instruction.ErrInvalidSyntax},
 	}
 
 	ctx, _ := instruction.CreateContext("apt-get", "")
@@ -64,7 +64,11 @@ func TestInstructionSyntax(t *testing.T) {
 		// no error expected
 		if test.Err == nil {
 			if err != nil {
-				lineerr := err.(LineError)
+				lineerr, ok := err.(LineError)
+				if !ok {
+					t.Errorf("[%d] expect error to be of type <LineError>", i)
+					continue
+				}
 				t.Errorf("[%d] expect no error, got <%s>", i, lineerr.Err)
 			}
 			continue