diff --git a/library/constant_time.c b/library/constant_time.c
index cb5003d..4b71a3d 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -82,7 +82,7 @@
 #elif defined(MBEDTLS_CT_AARCH64_ASM)
     asm volatile ("ldr %w0, [%1]" : "=r" (r) : MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT(p) :);
 #else
-#error No assembly defined for mbedtls_get_unaligned_volatile_uint32
+#error "No assembly defined for mbedtls_get_unaligned_volatile_uint32"
 #endif
     return r;
 }