diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index 8b8629b94..c3b192d44 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -116,6 +116,8 @@ var knownFunctions = map[string]interface {
 	"sort":     &simpleCallParser{name: baseName + ".mksort", returnType: starlarkTypeList},
 	"strip":    &simpleCallParser{name: baseName + ".mkstrip", returnType: starlarkTypeString},
 	"subst":    &substCallParser{fname: "subst"},
+	"to-lower": &lowerUpperParser{isUpper: false},
+	"to-upper": &lowerUpperParser{isUpper: true},
 	"warning":  &makeControlFuncParser{name: baseName + ".mkwarning"},
 	"word":     &wordCallParser{},
 	"words":    &wordsCallParser{},
@@ -1895,6 +1897,24 @@ func (p *evalNodeParser) parse(ctx *parseContext, node mkparser.Node, args *mkpa
 	return []starlarkNode{ctx.newBadNode(node, "Eval expression too complex; only assignments, comments, includes, and inherit-products are supported")}
 }
 
+type lowerUpperParser struct {
+	isUpper bool
+}
+
+func (p *lowerUpperParser) parse(ctx *parseContext, node mkparser.Node, args *mkparser.MakeString) starlarkExpr {
+	fn := "lower"
+	if p.isUpper {
+		fn = "upper"
+	}
+	arg := ctx.parseMakeString(node, args)
+
+	return &callExpr{
+		object:     arg,
+		name:       fn,
+		returnType: starlarkTypeString,
+	}
+}
+
 func (ctx *parseContext) parseMakeString(node mkparser.Node, mk *mkparser.MakeString) starlarkExpr {
 	if mk.Const() {
 		return &stringLiteralExpr{mk.Dump()}
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 7e14e259d..65a3be7f7 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1659,6 +1659,26 @@ def init(g, handle):
   g["X"] = "%s Y" % g.get("A", "") or g["B"]
   g["D"] = rblf.expand_wildcard("*.mk")
   g["X"] = rblf.mk2rbc_error("product.mk:12", "Expected all arguments to $(or) or $(and) to have the same type, found \"string\" and \"list\"")
+`,
+	},
+	{
+
+		desc:   "is-lower/is-upper",
+		mkname: "product.mk",
+		in: `
+X := $(call to-lower,aBc)
+X := $(call to-upper,aBc)
+X := $(call to-lower,$(VAR))
+X := $(call to-upper,$(VAR))
+`,
+		expected: `load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["X"] = ("aBc").lower()
+  g["X"] = ("aBc").upper()
+  g["X"] = (g.get("VAR", "")).lower()
+  g["X"] = (g.get("VAR", "")).upper()
 `,
 	},
 }