diff --git a/src/console_cmds.cpp b/src/console_cmds.cpp
index cf2444aac6..b5f8d2e47e 100644
--- a/src/console_cmds.cpp
+++ b/src/console_cmds.cpp
@@ -1268,7 +1268,7 @@ DEF_CONSOLE_CMD(ConRescanNewGRF)
 	}
 
 	TarScanner::DoScan();
-	ScanNewGRFFiles();
+	ScanNewGRFFiles(NULL);
 
 	return true;
 }
diff --git a/src/network/network_content_gui.cpp b/src/network/network_content_gui.cpp
index 498ef49180..3e901116d1 100644
--- a/src/network/network_content_gui.cpp
+++ b/src/network/network_content_gui.cpp
@@ -114,7 +114,7 @@ public:
 					break;
 
 				case CONTENT_TYPE_NEWGRF:
-					ScanNewGRFFiles();
+					ScanNewGRFFiles(NULL);
 					break;
 
 				case CONTENT_TYPE_SCENARIO:
diff --git a/src/newgrf_config.h b/src/newgrf_config.h
index 2561af1581..9d1f8c5072 100644
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -196,7 +196,7 @@ struct NewGRFScanCallback {
 	virtual void OnNewGRFsScanned() = 0;
 };
 
-void ScanNewGRFFiles(NewGRFScanCallback *callback = NULL);
+void ScanNewGRFFiles(NewGRFScanCallback *callback);
 void CheckForMissingSprites();
 const GRFConfig *FindGRFConfig(uint32 grfid, FindGRFConfigMode mode, const uint8 *md5sum = NULL, uint32 desired_version = 0);
 GRFConfig *GetGRFConfig(uint32 grfid, uint32 mask = 0xFFFFFFFF);