diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 503dea7fae..acffd84885 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -604,7 +604,7 @@ func (p *parser) typeDecl(group *Group) Decl {
 			} else {
 				// x is the array length expression
 				if debug && x == nil {
-					panic("internal error: nil expression")
+					panic("length expression is nil")
 				}
 				d.Type = p.arrayType(pos, x)
 			}
diff --git a/src/cmd/compile/internal/syntax/positions.go b/src/cmd/compile/internal/syntax/positions.go
index b00f86c67c..93596559a0 100644
--- a/src/cmd/compile/internal/syntax/positions.go
+++ b/src/cmd/compile/internal/syntax/positions.go
@@ -12,7 +12,7 @@ func StartPos(n Node) Pos {
 	for m := n; ; {
 		switch n := m.(type) {
 		case nil:
-			panic("internal error: nil")
+			panic("nil node")
 
 		// packages
 		case *File:
@@ -124,7 +124,7 @@ func EndPos(n Node) Pos {
 	for m := n; ; {
 		switch n := m.(type) {
 		case nil:
-			panic("internal error: nil")
+			panic("nil node")
 
 		// packages
 		case *File:
diff --git a/src/cmd/compile/internal/syntax/walk.go b/src/cmd/compile/internal/syntax/walk.go
index ef213daf7d..b025844204 100644
--- a/src/cmd/compile/internal/syntax/walk.go
+++ b/src/cmd/compile/internal/syntax/walk.go
@@ -70,7 +70,7 @@ type walker struct {
 
 func (w walker) node(n Node) {
 	if n == nil {
-		panic("invalid syntax tree: nil node")
+		panic("nil node")
 	}
 
 	w.v = w.v.Visit(n)