diff --git a/include/mbedtls/constant_time.h b/include/mbedtls/constant_time.h
index d31bff677e9d..cbc13c5cd154 100644
--- a/include/mbedtls/constant_time.h
+++ b/include/mbedtls/constant_time.h
@@ -9,6 +9,10 @@
 #ifndef MBEDTLS_CONSTANT_TIME_H
 #define MBEDTLS_CONSTANT_TIME_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stddef.h>
 
 /** Constant-time buffer comparison without branches.
@@ -33,4 +37,8 @@ int mbedtls_ct_memcmp(const void *a,
                       const void *b,
                       size_t n);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* MBEDTLS_CONSTANT_TIME_H */