diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index 646becbdae0..eae93309147 100644
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -312,6 +312,13 @@ func (check *Checker) typInternal(e0 syntax.Expr, def *Named) (T Type) {
 			typ := new(Pointer)
 			def.setUnderlying(typ)
 			typ.base = check.varType(e.X)
+			// If typ.base is invalid, it's unlikely that *base is particularly
+			// useful - even a valid dereferenciation will lead to an invalid
+			// type again, and in some cases we get unexpected follow-on errors
+			// (e.g., see #49005). Return an invalid type instead.
+			if typ.base == Typ[Invalid] {
+				return Typ[Invalid]
+			}
 			return typ
 		}
 
diff --git a/test/fixedbugs/issue49005a.go b/test/fixedbugs/issue49005a.go
new file mode 100644
index 00000000000..55d92c4650b
--- /dev/null
+++ b/test/fixedbugs/issue49005a.go
@@ -0,0 +1,13 @@
+// errorcheck
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T interface{ M() }
+
+func F() T
+
+var _ = F().(*X) // ERROR "undefined: X"