diff --git a/cc/config/riscv64_device.go b/cc/config/riscv64_device.go
index 67208b2..194b242 100644
--- a/cc/config/riscv64_device.go
+++ b/cc/config/riscv64_device.go
@@ -26,12 +26,16 @@
 		// Help catch common 32/64-bit errors.
 		"-Werror=implicit-function-declaration",
 		"-fno-emulated-tls",
+		// For -fsanitize=shadow-call-stack.
+		"-ffixed-x18",
 	}
 
 	riscv64ArchVariantCflags = map[string][]string{}
 
 	riscv64Ldflags = []string{
 		"-Wl,--hash-style=gnu",
+		// For -fsanitize=shadow-call-stack.
+		"-ffixed-x18",
 	}
 
 	riscv64Lldflags = append(riscv64Ldflags,