diff --git a/library/aes.c b/library/aes.c
index b55c08a..fa773ec 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -1866,7 +1866,7 @@
 #elif MBEDTLS_AESNI_HAVE_CODE == 2
         mbedtls_printf("  AES note: AESNI code present (intrinsics implementation).\n");
 #else
-#error Unrecognised value for MBEDTLS_AESNI_HAVE_CODE
+#error "Unrecognised value for MBEDTLS_AESNI_HAVE_CODE"
 #endif
         if (mbedtls_aesni_has_support(MBEDTLS_AESNI_AES)) {
             mbedtls_printf("  AES note: using AESNI.\n");
diff --git a/library/common.h b/library/common.h
index 97dc1d3..3c472c6 100644
--- a/library/common.h
+++ b/library/common.h
@@ -288,7 +288,7 @@
 /* Normal case (64-bit pointers): use "r" as the constraint for pointer operands to asm */
 #define MBEDTLS_ASM_AARCH64_PTR_CONSTRAINT "r"
 #else
-#error Unrecognised pointer size for aarch64
+#error "Unrecognised pointer size for aarch64"
 #endif
 #endif
 
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;
 }
diff --git a/library/entropy_poll.c b/library/entropy_poll.c
index f90167c..bc71307 100644
--- a/library/entropy_poll.c
+++ b/library/entropy_poll.c
@@ -75,7 +75,7 @@
     return 0;
 }
 #else /* !_WIN32_WINNT_WINXP */
-#error Entropy not available before Windows XP, use MBEDTLS_NO_PLATFORM_ENTROPY
+#error "Entropy not available before Windows XP, use MBEDTLS_NO_PLATFORM_ENTROPY"
 #endif /* !_WIN32_WINNT_WINXP */
 #else /* _WIN32 && !EFIX64 && !EFI32 */
 
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.
diff --git a/library/x509_crt.c b/library/x509_crt.c
index b40bad2..2cbced2 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1599,7 +1599,7 @@
 cleanup:
     FindClose(hFind);
 #else /* !_WIN32_WINNT_XP */
-#error mbedtls_x509_crt_parse_path not available before Windows XP
+#error "mbedtls_x509_crt_parse_path not available before Windows XP"
 #endif /* !_WIN32_WINNT_XP */
 #else /* _WIN32 */
     int t_ret;