diff --git a/base/cvd/cuttlefish/host/commands/assemble_cvd/assemble_cvd_flags.cpp b/base/cvd/cuttlefish/host/commands/assemble_cvd/assemble_cvd_flags.cpp
index b955a56653b..0ec1b308dfa 100644
--- a/base/cvd/cuttlefish/host/commands/assemble_cvd/assemble_cvd_flags.cpp
+++ b/base/cvd/cuttlefish/host/commands/assemble_cvd/assemble_cvd_flags.cpp
@@ -54,10 +54,12 @@ DEFINE_string(overlays, "",
               "vm_index2:display_index2 [...]'");
 DEFINE_string(extra_kernel_cmdline, CF_DEFAULTS_EXTRA_KERNEL_CMDLINE,
               "Additional flags to put on the kernel command line");
-DEFINE_string(extra_bootconfig_args, CF_DEFAULTS_EXTRA_BOOTCONFIG_ARGS,
+DEFINE_vec(extra_bootconfig_args, CF_DEFAULTS_EXTRA_BOOTCONFIG_ARGS,
               "Space-separated list of extra bootconfig args. "
               "Note: overwriting an existing bootconfig argument "
-              "requires ':=' instead of '='.");
+              "requires ':=' instead of '='. "
+              "If multiple instances are used, use comma as a separator "
+              "for each instance.");
 DEFINE_vec(guest_enforce_security,
            fmt::format("{}", CF_DEFAULTS_GUEST_ENFORCE_SECURITY),
            "Whether to run in enforcing mode (non permissive).");
diff --git a/base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc b/base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc
index 1cac6ede01d..09592d59dc2 100644
--- a/base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc
+++ b/base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc
@@ -532,6 +532,8 @@ Result<CuttlefishConfig> InitializeCuttlefishConfiguration(
 
   std::vector<std::string> extra_bootconfig_args_base64_vec =
       CF_EXPECT(GET_FLAG_STR_VALUE(extra_bootconfig_args_base64));
+  std::vector<std::string> extra_bootconfig_args_vec =
+      CF_EXPECT(GET_FLAG_STR_VALUE(extra_bootconfig_args));
 
   std::vector<bool> record_screen_vec = CF_EXPECT(GET_FLAG_BOOL_VALUE(
       record_screen));
@@ -795,7 +797,8 @@ Result<CuttlefishConfig> InitializeCuttlefishConfiguration(
     instance.set_enable_gnss_grpc_proxy(start_gnss_proxy_vec[instance_index]);
     instance.set_enable_bootanimation(enable_bootanimation_vec[instance_index]);
 
-    instance.set_extra_bootconfig_args(FLAGS_extra_bootconfig_args);
+    instance.set_extra_bootconfig_args(
+        extra_bootconfig_args_vec[instance_index]);
     if (!extra_bootconfig_args_base64_vec[instance_index].empty()) {
       std::vector<uint8_t> decoded_args;
       CF_EXPECT(DecodeBase64(extra_bootconfig_args_base64_vec[instance_index],