diff --git a/mbedtls-platform-support/Cargo.toml b/mbedtls-platform-support/Cargo.toml
index 72c2c0cb7..129e93c93 100644
--- a/mbedtls-platform-support/Cargo.toml
+++ b/mbedtls-platform-support/Cargo.toml
@@ -22,7 +22,7 @@ links = "mbedtls-platform-support"
 cfg-if = "1.0.0"
 spin = { version = "0.4.0", default-features = false, optional = true }
 chrono = { version = "0.4", optional = true }
-once_cell = "1.17.1"
+once_cell = { version = "1.17.1", optional = true }
 
 [target.x86_64-fortanix-unknown-sgx.dependencies]
 chrono = "0.4"
@@ -42,5 +42,5 @@ time = ["mbedtls-sys-auto/time"]
 std = ["mbedtls-sys-auto/std"]
 force_aesni_support = ["mbedtls-sys-auto/custom_has_support", "mbedtls-sys-auto/aes_alt", "aesni"]
 aesni = ["mbedtls-sys-auto/aesni"]
-tls13 = ["mbedtls-sys-auto/tls13"]
+tls13 = ["mbedtls-sys-auto/tls13", "once_cell"]
 rdrand = []