diff --git a/src/cmd/compile/internal/noder/transform.go b/src/cmd/compile/internal/noder/transform.go
index a673484821..6f49106f5e 100644
--- a/src/cmd/compile/internal/noder/transform.go
+++ b/src/cmd/compile/internal/noder/transform.go
@@ -115,6 +115,31 @@ func transformConv(n *ir.ConvExpr) ir.Node {
 		if n.X.Op() == ir.OLITERAL {
 			return stringtoruneslit(n)
 		}
+
+	case ir.OBYTES2STR:
+		assert(t.IsSlice())
+		assert(t.Elem().Kind() == types.TUINT8)
+		if t.Elem() != types.ByteType && t.Elem() != types.Types[types.TUINT8] {
+			// If t is a slice of a user-defined byte type B (not uint8
+			// or byte), then add an extra CONVNOP from []B to []byte, so
+			// that the call to slicebytetostring() added in walk will
+			// typecheck correctly.
+			n.X = ir.NewConvExpr(n.X.Pos(), ir.OCONVNOP, types.NewSlice(types.ByteType), n.X)
+			n.X.SetTypecheck(1)
+		}
+
+	case ir.ORUNES2STR:
+		assert(t.IsSlice())
+		assert(t.Elem().Kind() == types.TINT32)
+		if t.Elem() != types.RuneType && t.Elem() != types.Types[types.TINT32] {
+			// If t is a slice of a user-defined rune type B (not uint32
+			// or rune), then add an extra CONVNOP from []B to []rune, so
+			// that the call to slicerunetostring() added in walk will
+			// typecheck correctly.
+			n.X = ir.NewConvExpr(n.X.Pos(), ir.OCONVNOP, types.NewSlice(types.RuneType), n.X)
+			n.X.SetTypecheck(1)
+		}
+
 	}
 	return n
 }
diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 9b74bf7a9d..eb316d33db 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -466,6 +466,27 @@ func tcConv(n *ir.ConvExpr) ir.Node {
 		if n.X.Op() == ir.OLITERAL {
 			return stringtoruneslit(n)
 		}
+
+	case ir.OBYTES2STR:
+		if t.Elem() != types.ByteType && t.Elem() != types.Types[types.TUINT8] {
+			// If t is a slice of a user-defined byte type B (not uint8
+			// or byte), then add an extra CONVNOP from []B to []byte, so
+			// that the call to slicebytetostring() added in walk will
+			// typecheck correctly.
+			n.X = ir.NewConvExpr(n.X.Pos(), ir.OCONVNOP, types.NewSlice(types.ByteType), n.X)
+			n.X.SetTypecheck(1)
+		}
+
+	case ir.ORUNES2STR:
+		if t.Elem() != types.RuneType && t.Elem() != types.Types[types.TINT32] {
+			// If t is a slice of a user-defined rune type B (not uint32
+			// or rune), then add an extra CONVNOP from []B to []rune, so
+			// that the call to slicerunetostring() added in walk will
+			// typecheck correctly.
+			n.X = ir.NewConvExpr(n.X.Pos(), ir.OCONVNOP, types.NewSlice(types.RuneType), n.X)
+			n.X.SetTypecheck(1)
+		}
+
 	}
 	return n
 }
diff --git a/test/fixedbugs/issue23536.go b/test/fixedbugs/issue23536.go
new file mode 100644
index 0000000000..07b5033d36
--- /dev/null
+++ b/test/fixedbugs/issue23536.go
@@ -0,0 +1,22 @@
+// run
+
+// 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.
+
+// Test case where a slice of a user-defined byte type (not uint8 or byte) is
+// converted to a string.  Same for slice of runes.
+
+package main
+
+type MyByte byte
+
+type MyRune rune
+
+func main() {
+	var y []MyByte
+	_ = string(y)
+
+	var z []MyRune
+	_ = string(z)
+}
diff --git a/test/typeparam/issue23536.go b/test/typeparam/issue23536.go
new file mode 100644
index 0000000000..a4f061802f
--- /dev/null
+++ b/test/typeparam/issue23536.go
@@ -0,0 +1,32 @@
+// run -gcflags=-G=3
+
+// 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.
+
+// Test case where a slice of a user-defined byte type (not uint8 or byte) is
+// converted to a string.  Same for slice of runes.
+
+package main
+
+type MyByte byte
+
+type MyRune rune
+
+func f[T []MyByte](x T) string {
+	return string(x)
+}
+
+func g[T []MyRune](x T) string {
+	return string(x)
+}
+
+func main() {
+	var y []MyByte
+	_ = f(y)
+	_ = string(y)
+
+	var z []MyRune
+	_ = g(z)
+	_ = string(z)
+}