diff --git a/openssl-sys/src/lib.rs b/openssl-sys/src/lib.rs
index eca08b70..17c2864d 100644
--- a/openssl-sys/src/lib.rs
+++ b/openssl-sys/src/lib.rs
@@ -1623,7 +1623,7 @@ extern {
     pub fn SSL_CTX_use_PrivateKey(ctx: *mut SSL_CTX, key: *mut EVP_PKEY) -> c_int;
     pub fn SSL_CTX_check_private_key(ctx: *const SSL_CTX) -> c_int;
     pub fn SSL_CTX_set_client_CA_list(ctx: *mut SSL_CTX, list: *mut stack_st_X509_NAME);
-    pub fn SSL_CTX_get_cert_store(ctx: *mut SSL_CTX) -> *mut X509_STORE;
+    pub fn SSL_CTX_get_cert_store(ctx: *const SSL_CTX) -> *mut X509_STORE;
 
     #[cfg(not(ossl101))]
     pub fn SSL_CTX_get0_certificate(ctx: *const SSL_CTX) -> *mut X509;