diff --git a/src/http.h b/src/http.h
index c93b8c2f..828cee05 100644
--- a/src/http.h
+++ b/src/http.h
@@ -29,6 +29,6 @@
 #include <stdio.h>
 #include "protocol.h"
 
-const struct Protocol *const http_protocol;
+extern const struct Protocol *const http_protocol;
 
 #endif
diff --git a/src/tls.h b/src/tls.h
index 9b3b1c4d..14602c33 100644
--- a/src/tls.h
+++ b/src/tls.h
@@ -28,6 +28,6 @@
 
 #include "protocol.h"
 
-const struct Protocol *const tls_protocol;
+extern const struct Protocol *const tls_protocol;
 
 #endif