diff --git a/lib/curl_schannel.c b/lib/curl_schannel.c
index 7dd227ea4e4206e9d220a41893fa5473dae6f69b..6bab84b2a6309c8c4d793f45a84826ca14f610c5 100644
--- a/lib/curl_schannel.c
+++ b/lib/curl_schannel.c
@@ -965,12 +965,12 @@ void Curl_schannel_session_free(void *ptr)
   }
 }
 
-int Curl_schannel_init()
+int Curl_schannel_init(void)
 {
   return (Curl_sspi_global_init() == CURLE_OK ? 1 : 0);
 }
 
-void Curl_schannel_cleanup()
+void Curl_schannel_cleanup(void)
 {
   Curl_sspi_global_cleanup();
 }
diff --git a/lib/curl_schannel.h b/lib/curl_schannel.h
index bac6e422bebaf16b43bac4928b5853c5e7c216a1..2869b9263a1fe4f23eaabc3463aa2f5ee8056c79 100644
--- a/lib/curl_schannel.h
+++ b/lib/curl_schannel.h
@@ -108,8 +108,8 @@ void Curl_schannel_close(struct connectdata *conn, int sockindex);
 int Curl_schannel_shutdown(struct connectdata *conn, int sockindex);
 void Curl_schannel_session_free(void *ptr);
 
-int Curl_schannel_init();
-void Curl_schannel_cleanup();
+int Curl_schannel_init(void);
+void Curl_schannel_cleanup(void);
 size_t Curl_schannel_version(char *buffer, size_t size);
 
 /* API setup for Schannel */