diff --git a/src/cmd/compile/internal/types2/infer.go b/src/cmd/compile/internal/types2/infer.go
index 29633028f3..e131077371 100644
--- a/src/cmd/compile/internal/types2/infer.go
+++ b/src/cmd/compile/internal/types2/infer.go
@@ -739,8 +739,6 @@ func (w *cycleFinder) typ(typ Type) {
 	//      in signatures where they are handled explicitly.
 
 	case *Signature:
-		// There are no "method types" so we should never see a recv.
-		assert(t.recv == nil)
 		if t.params != nil {
 			w.varList(t.params.vars)
 		}
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue51593.go2 b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue51593.go2
new file mode 100644
index 0000000000..d323618ee8
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue51593.go2
@@ -0,0 +1,13 @@
+// Copyright 2022 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
+
+func f[P interface{ m(R) }, R any]() {}
+
+type T = interface { m(int) }
+
+func _() {
+	_ = f[ /* ERROR cannot infer R */ T] // don't crash in type inference
+}
diff --git a/src/go/types/infer.go b/src/go/types/infer.go
index 429510291e..6bed55c270 100644
--- a/src/go/types/infer.go
+++ b/src/go/types/infer.go
@@ -738,8 +738,6 @@ func (w *cycleFinder) typ(typ Type) {
 	//      in signatures where they are handled explicitly.
 
 	case *Signature:
-		// There are no "method types" so we should never see a recv.
-		assert(t.recv == nil)
 		if t.params != nil {
 			w.varList(t.params.vars)
 		}
diff --git a/src/go/types/testdata/fixedbugs/issue51593.go2 b/src/go/types/testdata/fixedbugs/issue51593.go2
new file mode 100644
index 0000000000..e06c39fac0
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue51593.go2
@@ -0,0 +1,13 @@
+// Copyright 2022 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
+
+func f[P interface{ m(R) }, R any]() {}
+
+type T = interface { m(int) }
+
+func _() {
+	_ = f /* ERROR cannot infer R */ [T] // don't crash in type inference
+}