diff --git a/src/cmd/asm/internal/asm/asm.go b/src/cmd/asm/internal/asm/asm.go
index dfb7ad19cce..63adef271be 100644
--- a/src/cmd/asm/internal/asm/asm.go
+++ b/src/cmd/asm/internal/asm/asm.go
@@ -11,6 +11,7 @@ import (
 
 	"cmd/asm/internal/addr"
 	"cmd/asm/internal/arch"
+	"cmd/asm/internal/flags"
 	"cmd/asm/internal/lex"
 	"cmd/internal/obj"
 )
@@ -140,7 +141,9 @@ func (p *Parser) append(prog *obj.Prog, doLabel bool) {
 		p.pendingLabels = p.pendingLabels[0:0]
 	}
 	prog.Pc = int64(p.pc)
-	fmt.Println(p.histLineNum, prog)
+	if *flags.Debug {
+		fmt.Println(p.histLineNum, prog)
+	}
 }
 
 // asmText assembles a TEXT pseudo-op.
diff --git a/src/cmd/asm/internal/flags/flags.go b/src/cmd/asm/internal/flags/flags.go
index 61cd860cd16..9640f994d7c 100644
--- a/src/cmd/asm/internal/flags/flags.go
+++ b/src/cmd/asm/internal/flags/flags.go
@@ -14,8 +14,9 @@ import (
 )
 
 var (
-	OutputFile = flag.String("o", "", "output file; default foo.6 for /a/b/c/foo.s on arm64 (unused TODO)")
-	PrintOut   = flag.Bool("S", true, "print assembly and machine code") // TODO: set to false
+	Debug      = flag.Bool("debug", false, "dump instructions as they are parsed")
+	OutputFile = flag.String("o", "", "output file; default foo.6 for /a/b/c/foo.s on amd64")
+	PrintOut   = flag.Bool("S", false, "print assembly and machine code")
 	TrimPath   = flag.String("trimpath", "", "remove prefix from recorded source file paths (unused TODO)")
 )
 
diff --git a/src/cmd/asm/main.go b/src/cmd/asm/main.go
index 3c02d4eebd5..937b1921781 100644
--- a/src/cmd/asm/main.go
+++ b/src/cmd/asm/main.go
@@ -54,7 +54,7 @@ func main() {
 	var ok bool
 	pList.Firstpc, ok = parser.Parse()
 	if !ok {
-		log.Print("FAIL TODO")
+		log.Fatalf("asm: assembly of %s failed", flag.Arg(0))
 		os.Exit(1)
 	}
 	obj.Writeobjdirect(ctxt, output)