diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 6d3359ad0e..a7349a8f1f 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -1349,6 +1349,16 @@ func (s *state) expr(n *Node) *ssa.Value {
 			return s.newValue1(op, Types[TINT], s.expr(n.Left))
 		case n.Left.Type.IsString(): // string; not reachable for OCAP
 			return s.newValue1(ssa.OpStringLen, Types[TINT], s.expr(n.Left))
+		case n.Left.Type.IsMap():
+			s.Unimplementedf("unhandled len(map)")
+			return nil
+		case n.Left.Type.IsChan():
+			if n.Op == OCAP {
+				s.Unimplementedf("unhandled cap(chan)")
+			} else {
+				s.Unimplementedf("unhandled len(chan)")
+			}
+			return nil
 		default: // array
 			return s.constInt(Types[TINT], n.Left.Type.Bound)
 		}
diff --git a/src/cmd/compile/internal/gc/type.go b/src/cmd/compile/internal/gc/type.go
index bcad025ba6..697152bebd 100644
--- a/src/cmd/compile/internal/gc/type.go
+++ b/src/cmd/compile/internal/gc/type.go
@@ -64,6 +64,14 @@ func (t *Type) IsString() bool {
 	return t.Etype == TSTRING
 }
 
+func (t *Type) IsMap() bool {
+	return t.Etype == TMAP
+}
+
+func (t *Type) IsChan() bool {
+	return t.Etype == TCHAN
+}
+
 func (t *Type) IsSlice() bool {
 	return t.Etype == TARRAY && t.Bound < 0
 }