diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index 024311e..2a80e56 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -1629,6 +1629,13 @@
 		return
 	}
 	if p, ok := maybeTrim(annotation, "include_top"); ok {
+		// Don't allow duplicate include tops, because then we will generate
+		// invalid starlark code. (duplicate keys in the _entry dictionary)
+		for _, top := range ctx.includeTops {
+			if top == p {
+				return
+			}
+		}
 		ctx.includeTops = append(ctx.includeTops, p)
 		return
 	}
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 94c4fe6..1e53c30 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1078,6 +1078,40 @@
 `,
 	},
 	{
+		desc:   "Dynamic inherit with duplicated hint",
+		mkname: "product.mk",
+		in: `
+MY_PATH:=foo
+#RBC# include_top vendor/foo1
+$(call inherit-product,$(MY_PATH)/cfg.mk)
+#RBC# include_top vendor/foo1
+$(call inherit-product,$(MY_PATH)/cfg.mk)
+`,
+		expected: `load("//build/make/core:product_config.rbc", "rblf")
+load("//vendor/foo1:cfg.star|init", _cfg_init = "init")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["MY_PATH"] = "foo"
+  #RBC# include_top vendor/foo1
+  _entry = {
+    "vendor/foo1/cfg.mk": ("_cfg", _cfg_init),
+  }.get("%s/cfg.mk" % g["MY_PATH"])
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("cannot")
+  rblf.inherit(handle, _varmod, _varmod_init)
+  #RBC# include_top vendor/foo1
+  _entry = {
+    "vendor/foo1/cfg.mk": ("_cfg", _cfg_init),
+  }.get("%s/cfg.mk" % g["MY_PATH"])
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("cannot")
+  rblf.inherit(handle, _varmod, _varmod_init)
+`,
+	},
+	{
 		desc:   "Ignore make rules",
 		mkname: "product.mk",
 		in: `