diff --git a/main.cc b/main.cc
index 5079568..316780c 100644
--- a/main.cc
+++ b/main.cc
@@ -327,7 +327,8 @@ struct ObState {
         }
     }
 
-    void rule_dup(const char *tgt, const char *ptgt, const char *dep) {
+    void rule_dup(ConstCharRange tgt, ConstCharRange ptgt, ConstCharRange dep,
+                  bool inherit_deps) {
         Rule *oldr = nullptr;
         for (auto &rule: rules.iter())
             if (ptgt == rule.target)
@@ -338,7 +339,7 @@ struct ObState {
         r.target = tgt;
         r.action = oldr->action;
         r.func = oldr->func;
-        r.deps = dep ? cscript::util::list_explode(dep) : oldr->deps;
+        r.deps = inherit_deps ? oldr->deps : cscript::util::list_explode(dep);
     }
 };
 
@@ -443,7 +444,7 @@ int main(int argc, char **argv) {
     os.cs.add_command("duprule", "sssN", [](CsState &cs, const char *tgt,
                                             const char *ptgt, const char *dep,
                                             int *numargs) {
-        ((ObState &)cs).rule_dup(tgt, ptgt, (*numargs > 2) ? dep : nullptr);
+        ((ObState &)cs).rule_dup(tgt, ptgt, dep, *numargs <= 2);
     });
 
     os.cs.add_commandn("getenv", "ss", [](CsState &cs, TvalRange args) {