diff --git a/python/servo/bootstrap_commands.py b/python/servo/bootstrap_commands.py
index 7f0be395d731..7382668ce57e 100644
--- a/python/servo/bootstrap_commands.py
+++ b/python/servo/bootstrap_commands.py
@@ -27,7 +27,7 @@
 )
 
 import servo.bootstrap as bootstrap
-from servo.command_base import CommandBase, BIN_SUFFIX, cd
+from servo.command_base import CommandBase, BIN_SUFFIX, cd, has_rustc_alt_build
 from servo.util import delete, download_bytes, download_file, extract, host_triple
 
 
@@ -67,6 +67,9 @@ def bootstrap(self, force=False):
                      action='store_true',
                      help='Use stable rustc version')
     def bootstrap_rustc(self, force=False, target=[], stable=False):
+        # Set default value for llvm-assertions when target platform is specified
+        if "SERVO_RUSTC_LLVM_ASSERTIONS" not in os.environ and target:
+            self.config["build"]["llvm-assertions"] = not has_rustc_alt_build(target)
         self.set_use_stable_rust(stable)
         version = self.rust_version()
         rust_path = self.rust_path()
diff --git a/python/servo/command_base.py b/python/servo/command_base.py
index e8bad0a742f6..af723f8988f5 100644
--- a/python/servo/command_base.py
+++ b/python/servo/command_base.py
@@ -201,6 +201,14 @@ def set_osmesa_env(bin_path, env):
     return env
 
 
+def has_rustc_alt_build(platform_or_triple):
+    platforms_with_rustc_alt_builds = ["unknown-linux-gnu", "apple-darwin", "pc-windows-msvc"]
+    for platform in platforms_with_rustc_alt_builds:
+        if platform in platform_or_triple:
+            return True
+    return False
+
+
 class BuildNotFound(Exception):
     def __init__(self, message):
         self.message = message
@@ -261,9 +269,8 @@ def resolverelative(category, key):
         self.config["tools"].setdefault("rustc-with-gold", get_env_bool("SERVO_RUSTC_WITH_GOLD", True))
 
         # https://github.com/rust-lang/rust/pull/39754
-        platforms_with_rustc_alt_builds = ["unknown-linux-gnu", "apple-darwin", "pc-windows-msvc"]
         llvm_assertions_default = ("SERVO_RUSTC_LLVM_ASSERTIONS" in os.environ
-                                   or host_platform() not in platforms_with_rustc_alt_builds)
+                                   or not has_rustc_alt_build(host_platform()))
 
         self.config.setdefault("build", {})
         self.config["build"].setdefault("android", False)