diff --git a/src/crypto_openssl.c b/src/crypto_openssl.c
index b48f982a..910e113f 100644
--- a/src/crypto_openssl.c
+++ b/src/crypto_openssl.c
@@ -37,6 +37,7 @@
 #include <openssl/rand.h>
 #include <openssl/evp.h>
 #include <openssl/hmac.h>
+#include <openssl/err.h>
 
 typedef struct {
   EVP_CIPHER *evp_cipher;