diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index dc383bc..58e8a8a 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -129,6 +129,9 @@
     (void) hash_alg;
     return global_data.drivers_initialized;
 }
+#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR) ||       \
+    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY) ||     \
+    defined(PSA_WANT_KEY_TYPE_DH_KEY_PAIR)
 static int psa_is_dh_key_size_valid(size_t bits)
 {
     if (bits != 2048 && bits != 3072 && bits != 4096 &&
@@ -138,6 +141,9 @@
 
     return 1;
 }
+#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR ||
+          MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY ||
+          PSA_WANT_KEY_TYPE_DH_KEY_PAIR */
 
 psa_status_t mbedtls_to_psa_error(int ret)
 {