diff --git a/cc/config/x86_darwin_host.go b/cc/config/x86_darwin_host.go
index 65fa1ed..bb751fe 100644
--- a/cc/config/x86_darwin_host.go
+++ b/cc/config/x86_darwin_host.go
@@ -159,6 +159,8 @@
 		strings.Join(ClangFilterUnknownCflags(darwinX8664Cflags), " "))
 	pctx.StaticVariable("DarwinX86ClangLdflags", strings.Join(darwinX86ClangLdflags, " "))
 	pctx.StaticVariable("DarwinX8664ClangLdflags", strings.Join(darwinX8664ClangLdflags, " "))
+	pctx.StaticVariable("DarwinX86YasmFlags", "-f macho -m x86")
+	pctx.StaticVariable("DarwinX8664YasmFlags", "-f macho -m amd64")
 }
 
 func xcrun(config android.Config, args ...string) (string, error) {
@@ -276,6 +278,14 @@
 	return "${config.DarwinClangLdflags} ${config.DarwinX8664ClangLdflags}"
 }
 
+func (t *toolchainDarwinX86) YasmFlags() string {
+	return "${config.DarwinX86YasmFlags}"
+}
+
+func (t *toolchainDarwinX8664) YasmFlags() string {
+	return "${config.DarwinX8664YasmFlags}"
+}
+
 func (t *toolchainDarwin) ShlibSuffix() string {
 	return ".dylib"
 }
diff --git a/cc/config/x86_linux_host.go b/cc/config/x86_linux_host.go
index 80e9289..65ac603 100644
--- a/cc/config/x86_linux_host.go
+++ b/cc/config/x86_linux_host.go
@@ -160,6 +160,9 @@
 	pctx.StaticVariable("LinuxX8664ClangLdflags", strings.Join(linuxX8664ClangLdflags, " "))
 	pctx.StaticVariable("LinuxX86ClangCppflags", strings.Join(linuxX86ClangCppflags, " "))
 	pctx.StaticVariable("LinuxX8664ClangCppflags", strings.Join(linuxX8664ClangCppflags, " "))
+	// Yasm flags
+	pctx.StaticVariable("LinuxX86YasmFlags", "-f elf32 -m x86")
+	pctx.StaticVariable("LinuxX8664YasmFlags", "-f elf64 -m amd64")
 }
 
 type toolchainLinux struct {
@@ -252,6 +255,14 @@
 	return "${config.LinuxClangLdflags} ${config.LinuxX8664ClangLdflags}"
 }
 
+func (t *toolchainLinuxX86) YasmFlags() string {
+	return "${config.LinuxX86YasmFlags}"
+}
+
+func (t *toolchainLinuxX8664) YasmFlags() string {
+	return "${config.LinuxX8664YasmFlags}"
+}
+
 func (t *toolchainLinux) AvailableLibraries() []string {
 	return linuxAvailableLibraries
 }