diff --git a/build/fbcode_builder/getdeps.py b/build/fbcode_builder/getdeps.py
index b72447d7e..6ee7fa7ac 100755
--- a/build/fbcode_builder/getdeps.py
+++ b/build/fbcode_builder/getdeps.py
@@ -7,6 +7,7 @@
 from __future__ import absolute_import, division, print_function, unicode_literals
 
 import argparse
+import json
 import os
 import shutil
 import subprocess
@@ -500,6 +501,12 @@ class BuildCmd(ProjectCmdBase):
                     if dep_build:
                         sources_changed = True
 
+                extra_cmake_defines = (
+                    json.loads(args.extra_cmake_defines)
+                    if args.extra_cmake_defines
+                    else {}
+                )
+
                 if sources_changed or reconfigure or not os.path.exists(built_marker):
                     if os.path.exists(built_marker):
                         os.unlink(built_marker)
@@ -512,6 +519,7 @@ class BuildCmd(ProjectCmdBase):
                         ctx,
                         loader,
                         final_install_prefix=loader.get_project_install_prefix(m),
+                        extra_cmake_defines=extra_cmake_defines,
                     )
                     builder.build(install_dirs, reconfigure=reconfigure)
 
@@ -639,6 +647,14 @@ class BuildCmd(ProjectCmdBase):
         parser.add_argument(
             "--schedule-type", help="Indicates how the build was activated"
         )
+        parser.add_argument(
+            "--extra-cmake-defines",
+            help=(
+                "Input json map that contains extra cmake defines to be used "
+                "when compiling the current project and all its deps. "
+                'e.g: \'{"CMAKE_CXX_FLAGS": "--bla"}\''
+            ),
+        )
 
 
 @cmd("fixup-dyn-deps", "Adjusts dynamic dependencies for packaging purposes")
diff --git a/build/fbcode_builder/getdeps/builder.py b/build/fbcode_builder/getdeps/builder.py
index 7012256a7..f50f374fa 100644
--- a/build/fbcode_builder/getdeps/builder.py
+++ b/build/fbcode_builder/getdeps/builder.py
@@ -387,6 +387,7 @@ if __name__ == "__main__":
         inst_dir,
         defines,
         final_install_prefix=None,
+        extra_cmake_defines=None,
     ):
         super(CMakeBuilder, self).__init__(
             build_opts,
@@ -398,6 +399,8 @@ if __name__ == "__main__":
             final_install_prefix=final_install_prefix,
         )
         self.defines = defines or {}
+        if extra_cmake_defines:
+            self.defines.update(extra_cmake_defines)
 
     def _invalidate_cache(self):
         for name in [
diff --git a/build/fbcode_builder/getdeps/buildopts.py b/build/fbcode_builder/getdeps/buildopts.py
index 8620c8126..993a3ba01 100644
--- a/build/fbcode_builder/getdeps/buildopts.py
+++ b/build/fbcode_builder/getdeps/buildopts.py
@@ -436,6 +436,10 @@ def setup_build_options(args, host_type=None):
     if not is_windows():
         scratch_dir = os.path.realpath(scratch_dir)
 
+    # Save any extra cmake defines passed by the user in an env variable, so it
+    # can be used while hashing this build.
+    os.environ["GETDEPS_CMAKE_DEFINES"] = getattr(args, "extra_cmake_defines", "") or ""
+
     host_type = _check_host_type(args, host_type)
 
     return BuildOptions(
diff --git a/build/fbcode_builder/getdeps/load.py b/build/fbcode_builder/getdeps/load.py
index 40685511c..22b653dea 100644
--- a/build/fbcode_builder/getdeps/load.py
+++ b/build/fbcode_builder/getdeps/load.py
@@ -275,7 +275,14 @@ class ManifestLoader(object):
         env["os"] = self.build_opts.host_type.ostype
         env["distro"] = self.build_opts.host_type.distro
         env["distro_vers"] = self.build_opts.host_type.distrovers
-        for name in ["CXXFLAGS", "CPPFLAGS", "LDFLAGS", "CXX", "CC"]:
+        for name in [
+            "CXXFLAGS",
+            "CPPFLAGS",
+            "LDFLAGS",
+            "CXX",
+            "CC",
+            "GETDEPS_CMAKE_DEFINES",
+        ]:
             env[name] = os.environ.get(name)
         for tool in ["cc", "c++", "gcc", "g++", "clang", "clang++"]:
             env["tool-%s" % tool] = path_search(os.environ, tool)
diff --git a/build/fbcode_builder/getdeps/manifest.py b/build/fbcode_builder/getdeps/manifest.py
index 1e1526dcf..2c0ddecf4 100644
--- a/build/fbcode_builder/getdeps/manifest.py
+++ b/build/fbcode_builder/getdeps/manifest.py
@@ -420,6 +420,7 @@ class ManifestParser(object):
         ctx,
         loader,
         final_install_prefix=None,
+        extra_cmake_defines=None,
     ):
         builder = self.get("build", "builder", ctx=ctx)
         if not builder:
@@ -472,6 +473,7 @@ class ManifestParser(object):
                 inst_dir,
                 defines,
                 final_install_prefix,
+                extra_cmake_defines,
             )
 
         if builder == "python-wheel":