diff --git a/crypto/sha.h b/crypto/sha.h
index e65418cc..ea387c21 100644
--- a/crypto/sha.h
+++ b/crypto/sha.h
@@ -211,4 +211,7 @@ extern int hmacResult(HMACContext *context,
 
 void sha256_init_accel(void);
 
+/* Export for optimized version to silent -Wmissing-prototypes. */
+void sha256_process_x86(uint32_t state[8], const uint8_t data[], uint32_t length);
+
 #endif /* _SHA_H_ */
diff --git a/crypto/sha256-x86.c b/crypto/sha256-x86.c
index 602c53cf..57be3f0d 100644
--- a/crypto/sha256-x86.c
+++ b/crypto/sha256-x86.c
@@ -13,6 +13,8 @@
 # include <x86intrin.h>
 #endif
 
+#include "sha.h"
+
 /* Process multiple blocks. The caller is responsible for setting the initial */
 /*  state, and the caller is responsible for padding the final block.        */
 void sha256_process_x86(uint32_t state[8], const uint8_t data[], uint32_t length)