diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -32,8 +32,8 @@ GRFConfig *_grfconfig_static;
 static bool CalcGRFMD5Sum(GRFConfig *config)
 {
 	FILE *f;
-	md5_state_t md5state;
-	md5_byte_t buffer[1024];
+	Md5 checksum;
+	uint8 buffer[1024];
 	size_t len, size;
 
 	/* open the file */
@@ -41,12 +41,11 @@ static bool CalcGRFMD5Sum(GRFConfig *con
 	if (f == NULL) return false;
 
 	/* calculate md5sum */
-	md5_init(&md5state);
 	while ((len = fread(buffer, 1, (size > sizeof(buffer)) ? sizeof(buffer) : size, f)) != 0 && size != 0) {
 		size -= len;
-		md5_append(&md5state, buffer, len);
+		checksum.Append(buffer, len);
 	}
-	md5_finish(&md5state, config->md5sum);
+	checksum.Finish(config->md5sum);
 
 	FioFCloseFile(f);