diff --git a/library/psa_crypto_storage.h b/library/psa_crypto_storage.h
index 04768f8..edd9b94 100644
--- a/library/psa_crypto_storage.h
+++ b/library/psa_crypto_storage.h
@@ -39,7 +39,7 @@
 /* Sanity check: a file size must fit in 32 bits. Allow a generous
  * 64kB of metadata. */
 #if PSA_CRYPTO_MAX_STORAGE_SIZE > 0xffff0000
-#error PSA_CRYPTO_MAX_STORAGE_SIZE > 0xffff0000
+#error "PSA_CRYPTO_MAX_STORAGE_SIZE > 0xffff0000"
 #endif
 
 /** The maximum permitted persistent slot number.