diff --git a/src/newgrf.cpp b/src/newgrf.cpp
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -8718,18 +8718,18 @@ GRFFile::GRFFile(const GRFConfig *config
 	}
 
 	/* Initialise rail type map with default rail types */
-	memset(this->railtype_map, INVALID_RAILTYPE, sizeof(this->railtype_map));
+	std::fill(std::begin(this->railtype_map), std::end(this->railtype_map), INVALID_RAILTYPE);
 	this->railtype_map[0] = RAILTYPE_RAIL;
 	this->railtype_map[1] = RAILTYPE_ELECTRIC;
 	this->railtype_map[2] = RAILTYPE_MONO;
 	this->railtype_map[3] = RAILTYPE_MAGLEV;
 
 	/* Initialise road type map with default road types */
-	memset(this->roadtype_map, INVALID_ROADTYPE, sizeof(this->roadtype_map));
+	std::fill(std::begin(this->roadtype_map), std::end(this->roadtype_map), INVALID_ROADTYPE);
 	this->roadtype_map[0] = ROADTYPE_ROAD;
 
 	/* Initialise tram type map with default tram types */
-	memset(this->tramtype_map, INVALID_ROADTYPE, sizeof(this->tramtype_map));
+	std::fill(std::begin(this->tramtype_map), std::end(this->tramtype_map), INVALID_ROADTYPE);
 	this->tramtype_map[0] = ROADTYPE_TRAM;
 
 	/* Copy the initial parameter list