diff --git a/mypyc/build_setup.py b/mypyc/build_setup.py
index 2354853b3808..2c2cf56345c0 100644
--- a/mypyc/build_setup.py
+++ b/mypyc/build_setup.py
@@ -36,6 +36,7 @@
 ccompiler.CCompiler.__spawn = ccompiler.CCompiler.spawn  # type: ignore[attr-defined]
 X86_64 = platform.machine() in ("x86_64", "AMD64", "amd64")
 PYODIDE = "PYODIDE" in os.environ
+NO_EXTRA_FLAGS = "MYPYC_NO_EXTRA_FLAGS" in os.environ
 
 
 def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
@@ -46,7 +47,7 @@ def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
                 continue
             if "base64/arch/" in str(argument):
                 new_cmd.extend(["-msimd128"])
-    else:
+    elif not NO_EXTRA_FLAGS:
         compiler_type: str = self.compiler_type
         extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT.get(compiler_type, None)
         new_cmd = list(cmd)
diff --git a/mypyc/lib-rt/build_setup.py b/mypyc/lib-rt/build_setup.py
index 2354853b3808..2c2cf56345c0 100644
--- a/mypyc/lib-rt/build_setup.py
+++ b/mypyc/lib-rt/build_setup.py
@@ -36,6 +36,7 @@
 ccompiler.CCompiler.__spawn = ccompiler.CCompiler.spawn  # type: ignore[attr-defined]
 X86_64 = platform.machine() in ("x86_64", "AMD64", "amd64")
 PYODIDE = "PYODIDE" in os.environ
+NO_EXTRA_FLAGS = "MYPYC_NO_EXTRA_FLAGS" in os.environ
 
 
 def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
@@ -46,7 +47,7 @@ def spawn(self, cmd, **kwargs) -> None:  # type: ignore[no-untyped-def]
                 continue
             if "base64/arch/" in str(argument):
                 new_cmd.extend(["-msimd128"])
-    else:
+    elif not NO_EXTRA_FLAGS:
         compiler_type: str = self.compiler_type
         extra_options = EXTRA_FLAGS_PER_COMPILER_TYPE_PER_PATH_COMPONENT.get(compiler_type, None)
         new_cmd = list(cmd)