diff --git a/src/cmd/asm/internal/asm/parse.go b/src/cmd/asm/internal/asm/parse.go
index 4258c5ce26..6c324ce3af 100644
--- a/src/cmd/asm/internal/asm/parse.go
+++ b/src/cmd/asm/internal/asm/parse.go
@@ -297,7 +297,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 			p.errorf("illegal use of register list")
 		}
 		p.registerList(a)
-		p.expect(scanner.EOF)
+		p.expectOperandEnd()
 		return true
 	}
 
@@ -331,7 +331,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 			}
 		}
 		// fmt.Printf("REG %s\n", obj.Dconv(&emptyProg, 0, a))
-		p.expect(scanner.EOF)
+		p.expectOperandEnd()
 		return true
 	}
 
@@ -363,7 +363,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 			a.Type = obj.TYPE_FCONST
 			a.Val = p.floatExpr()
 			// fmt.Printf("FCONST %s\n", obj.Dconv(&emptyProg, 0, a))
-			p.expect(scanner.EOF)
+			p.expectOperandEnd()
 			return true
 		}
 		if p.have(scanner.String) {
@@ -378,7 +378,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 			a.Type = obj.TYPE_SCONST
 			a.Val = str
 			// fmt.Printf("SCONST %s\n", obj.Dconv(&emptyProg, 0, a))
-			p.expect(scanner.EOF)
+			p.expectOperandEnd()
 			return true
 		}
 		a.Offset = int64(p.expr())
@@ -392,7 +392,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 				a.Type = obj.TYPE_MEM
 			}
 			// fmt.Printf("CONST %d %s\n", a.Offset, obj.Dconv(&emptyProg, 0, a))
-			p.expect(scanner.EOF)
+			p.expectOperandEnd()
 			return true
 		}
 		// fmt.Printf("offset %d \n", a.Offset)
@@ -402,7 +402,7 @@ func (p *Parser) operand(a *obj.Addr) bool {
 	p.registerIndirect(a, prefix)
 	// fmt.Printf("DONE %s\n", p.arch.Dconv(&emptyProg, 0, a))
 
-	p.expect(scanner.EOF)
+	p.expectOperandEnd()
 	return true
 }
 
@@ -983,14 +983,19 @@ func (p *Parser) more() bool {
 
 // get verifies that the next item has the expected type and returns it.
 func (p *Parser) get(expected lex.ScanToken) lex.Token {
-	p.expect(expected)
+	p.expect(expected, expected.String())
 	return p.next()
 }
 
+// expectOperandEnd verifies that the parsing state is properly at the end of an operand.
+func (p *Parser) expectOperandEnd() {
+	p.expect(scanner.EOF, "end of operand")
+}
+
 // expect verifies that the next item has the expected type. It does not consume it.
-func (p *Parser) expect(expected lex.ScanToken) {
-	if p.peek() != expected {
-		p.errorf("expected %s, found %s", expected, p.next())
+func (p *Parser) expect(expectedToken lex.ScanToken, expectedMessage string) {
+	if p.peek() != expectedToken {
+		p.errorf("expected %s, found %s", expectedMessage, p.next())
 	}
 }
 
diff --git a/src/cmd/asm/internal/asm/pseudo_test.go b/src/cmd/asm/internal/asm/pseudo_test.go
index ee13b724eb..2e6d6c8154 100644
--- a/src/cmd/asm/internal/asm/pseudo_test.go
+++ b/src/cmd/asm/internal/asm/pseudo_test.go
@@ -35,8 +35,8 @@ func TestErroneous(t *testing.T) {
 		{"TEXT", "%", "expect two or three operands for TEXT"},
 		{"TEXT", "1, 1", "TEXT symbol \"<erroneous symbol>\" must be a symbol(SB)"},
 		{"TEXT", "$\"foo\", 0, $1", "TEXT symbol \"<erroneous symbol>\" must be a symbol(SB)"},
-		{"TEXT", "$0É:0, 0, $1", "expected EOF, found É"},   // Issue #12467.
-		{"TEXT", "$:0:(SB, 0, $1", "expected '(', found 0"}, // Issue 12468.
+		{"TEXT", "$0É:0, 0, $1", "expected end of operand, found É"}, // Issue #12467.
+		{"TEXT", "$:0:(SB, 0, $1", "expected '(', found 0"},          // Issue 12468.
 		{"FUNCDATA", "", "expect two operands for FUNCDATA"},
 		{"FUNCDATA", "(SB ", "expect two operands for FUNCDATA"},
 		{"DATA", "", "expect two operands for DATA"},
diff --git a/src/cmd/asm/internal/lex/input.go b/src/cmd/asm/internal/lex/input.go
index 33b9d8adea..4855daa892 100644
--- a/src/cmd/asm/internal/lex/input.go
+++ b/src/cmd/asm/internal/lex/input.go
@@ -30,7 +30,7 @@ type Input struct {
 	peekText        string
 }
 
-// NewInput returns a
+// NewInput returns an Input from the given path.
 func NewInput(name string) *Input {
 	return &Input{
 		// include directories: look in source dir, then -I directories.
diff --git a/src/cmd/asm/internal/lex/lex.go b/src/cmd/asm/internal/lex/lex.go
index 6fce55f7f4..81339059b1 100644
--- a/src/cmd/asm/internal/lex/lex.go
+++ b/src/cmd/asm/internal/lex/lex.go
@@ -77,7 +77,7 @@ func NewLexer(name string, ctxt *obj.Link) TokenReader {
 	input := NewInput(name)
 	fd, err := os.Open(name)
 	if err != nil {
-		log.Fatalf("asm: %s\n", err)
+		log.Fatalf("%s\n", err)
 	}
 	input.Push(NewTokenizer(name, fd, fd))
 	return input
diff --git a/src/cmd/asm/main.go b/src/cmd/asm/main.go
index f48050c137..4e450bec98 100644
--- a/src/cmd/asm/main.go
+++ b/src/cmd/asm/main.go
@@ -26,7 +26,7 @@ func main() {
 
 	architecture := arch.Set(GOARCH)
 	if architecture == nil {
-		log.Fatalf("asm: unrecognized architecture %s", GOARCH)
+		log.Fatalf("unrecognized architecture %s", GOARCH)
 	}
 
 	flags.Parse()
@@ -66,7 +66,7 @@ func main() {
 		obj.Writeobjdirect(ctxt, output)
 	}
 	if !ok || diag {
-		log.Printf("asm: assembly of %s failed", flag.Arg(0))
+		log.Printf("assembly of %s failed", flag.Arg(0))
 		os.Remove(*flags.OutputFile)
 		os.Exit(1)
 	}