diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index 94d1a6310..fe1cfb3a4 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -660,7 +660,7 @@ bool DecoSchematic::loadSchematicFile() {
 	std::ifstream is(filename.c_str(), std::ios_base::binary);
 
 	u32 signature = readU32(is);
-	if (signature != 'MTSM') {
+	if (signature != MTSCHEM_FILE_SIGNATURE) {
 		errorstream << "loadSchematicFile: invalid schematic "
 			"file" << std::endl;
 		return false;
@@ -719,7 +719,7 @@ bool DecoSchematic::loadSchematicFile() {
 void DecoSchematic::saveSchematicFile(INodeDefManager *ndef) {
 	std::ofstream os(filename.c_str(), std::ios_base::binary);
 
-	writeU32(os, 'MTSM'); // signature
+	writeU32(os, MTSCHEM_FILE_SIGNATURE); // signature
 	writeU16(os, 1);      // version
 	writeV3S16(os, size); // schematic size
 	
diff --git a/src/mapgen.h b/src/mapgen.h
index 7229e8996..2287445ee 100644
--- a/src/mapgen.h
+++ b/src/mapgen.h
@@ -260,6 +260,8 @@ class DecoSimple : public Decoration {
 	virtual std::string getName();
 };
 
+#define MTSCHEM_FILE_SIGNATURE 0x4d54534d // 'MTSM'
+
 enum Rotation {
 	ROTATE_0,
 	ROTATE_90,