diff --git a/go/types/testdata/decls0.src b/go/types/testdata/decls0.src
index 9da75b90..f1df3ea7 100644
--- a/go/types/testdata/decls0.src
+++ b/go/types/testdata/decls0.src
@@ -190,10 +190,11 @@ func (S0) m2(x *S0 /* ERROR "field or method" */ .m2) {}
 func (S0) m3() (x S0 /* ERROR "field or method" */ .m3) { return }
 func (S0) m4() (x *S0 /* ERROR "field or method" */ .m4) { return }
 
-// interfaces may have at most one blank method
+// interfaces may not have any blank methods
 type BlankI interface {
-	_()
-	_ /* ERROR redeclared */ ()
+	_ /* ERROR "invalid method name" */ ()
+	_ /* ERROR "invalid method name" */ (float32) int
+	m()
 }
 
 // non-interface types may have multiple blank methods
@@ -203,20 +204,3 @@ func (BlankT) _() {}
 func (BlankT) _(int) {}
 func (BlankT) _() int { return 0 }
 func (BlankT) _(int) int { return 0}
-
-// no type can ever satisfy an interface with a _ method
-func _() {
-	var i BlankI
-	var x BlankT
-	i = x /* ERROR "cannot assign" */
-	_ = i
-}
-
-// assignability of interfaces with blank methods
-func _() {
-	var x1, x1b interface { _() }
-	var x2 interface { _() }
-	x1 = x2
-	_ = x1
-	x1 = x1b
-}
\ No newline at end of file
diff --git a/go/types/typexpr.go b/go/types/typexpr.go
index 3c48c71c..f5a42cd2 100644
--- a/go/types/typexpr.go
+++ b/go/types/typexpr.go
@@ -472,6 +472,12 @@ func (check *checker) interfaceType(iface *Interface, ityp *ast.InterfaceType, d
 			// and we don't care if a constructed AST has more.
 			name := f.Names[0]
 			pos := name.Pos()
+			// spec: "As with all method sets, in an interface type,
+			// each method must have a unique non-blank name."
+			if name.Name == "_" {
+				check.errorf(pos, "invalid method name _")
+				continue
+			}
 			// Don't type-check signature yet - use an
 			// empty signature now and update it later.
 			// Since we know the receiver, set it up now
@@ -483,10 +489,6 @@ func (check *checker) interfaceType(iface *Interface, ityp *ast.InterfaceType, d
 			sig := new(Signature)
 			sig.recv = NewVar(pos, check.pkg, "", recvTyp)
 			m := NewFunc(pos, check.pkg, name.Name, sig)
-			// spec: "As with all method sets, in an interface type,
-			// each method must have a unique name."
-			// (The spec does not exclude blank _ identifiers for
-			// interface methods.)
 			if check.declareInSet(&mset, pos, m) {
 				iface.methods = append(iface.methods, m)
 				iface.allMethods = append(iface.allMethods, m)