diff --git a/library/psa_crypto_cipher.c b/library/psa_crypto_cipher.c
index 3f2ddbd..f4fc499 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -42,6 +42,63 @@
     psa_algorithm_t alg,
     psa_key_type_t key_type)
 {
+    /* Reduce code size - hinting to the compiler about what it can assume allows the compiler to
+       eliminate bits of the logic below. */
+#if !defined(PSA_WANT_KEY_TYPE_AES)
+    MBEDTLS_ASSUME(key_type != PSA_KEY_TYPE_AES);
+#endif
+#if !defined(PSA_WANT_KEY_TYPE_ARIA)
+    MBEDTLS_ASSUME(key_type != PSA_KEY_TYPE_ARIA);
+#endif
+#if !defined(PSA_WANT_KEY_TYPE_CAMELLIA)
+    MBEDTLS_ASSUME(key_type != PSA_KEY_TYPE_CAMELLIA);
+#endif
+#if !defined(PSA_WANT_KEY_TYPE_CHACHA20)
+    MBEDTLS_ASSUME(key_type != PSA_KEY_TYPE_CHACHA20);
+#endif
+#if !defined(PSA_WANT_KEY_TYPE_DES)
+    MBEDTLS_ASSUME(key_type != PSA_KEY_TYPE_DES);
+#endif
+#if !defined(PSA_WANT_ALG_CCM)
+    MBEDTLS_ASSUME(alg != PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_CCM, 0));
+#endif
+#if !defined(PSA_WANT_ALG_GCM)
+    MBEDTLS_ASSUME(alg != PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, 0));
+#endif
+#if !defined(PSA_WANT_ALG_STREAM_CIPHER)
+    MBEDTLS_ASSUME(alg != PSA_ALG_STREAM_CIPHER);
+#endif
+#if !defined(PSA_WANT_ALG_CHACHA20_POLY1305)
+    MBEDTLS_ASSUME(alg != PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_CHACHA20_POLY1305, 0));
+#endif
+#if !defined(PSA_WANT_ALG_CCM_STAR_NO_TAG)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CCM_STAR_NO_TAG);
+#endif
+#if !defined(PSA_WANT_ALG_CTR)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CTR);
+#endif
+#if !defined(PSA_WANT_ALG_CFB)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CFB);
+#endif
+#if !defined(PSA_WANT_ALG_OFB)
+    MBEDTLS_ASSUME(alg != PSA_ALG_OFB);
+#endif
+#if !defined(PSA_WANT_ALG_XTS)
+    MBEDTLS_ASSUME(alg != PSA_ALG_XTS);
+#endif
+#if !defined(PSA_WANT_ALG_ECB_NO_PADDING)
+    MBEDTLS_ASSUME(alg != PSA_ALG_ECB_NO_PADDING);
+#endif
+#if !defined(PSA_WANT_ALG_CBC_NO_PADDING)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CBC_NO_PADDING);
+#endif
+#if !defined(PSA_WANT_ALG_CBC_PKCS7)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CBC_PKCS7);
+#endif
+#if !defined(PSA_WANT_ALG_CMAC)
+    MBEDTLS_ASSUME(alg != PSA_ALG_CMAC);
+#endif
+
     if (alg == PSA_ALG_STREAM_CIPHER ||
         alg == PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_CHACHA20_POLY1305, 0)) {
         if (key_type == PSA_KEY_TYPE_CHACHA20) {