diff --git a/source/core/maptypes.h b/source/core/maptypes.h
index 04f4b026d..813836a37 100644
--- a/source/core/maptypes.h
+++ b/source/core/maptypes.h
@@ -294,8 +294,8 @@ struct walltype
 	bool hasX() const { return _xw != nullptr; }
 	void allocX();
 
-	FTextureID walltexture() const;
-	FTextureID overtexture() const;
+	const FTextureID walltexture() const;
+	const FTextureID overtexture() const;
 	void setwalltexture(FTextureID tex);
 	void setovertexture(FTextureID tex);
 };
@@ -501,7 +501,7 @@ struct spritetypebase
 		pos = { x * maptoworld, y * maptoworld, z * zmaptoworld };
 	}
 
-	FTextureID spritetexture() const;
+	const FTextureID spritetexture() const;
 };
 
 
diff --git a/source/core/textures/buildtiles.cpp b/source/core/textures/buildtiles.cpp
index 2de9360a2..2c5e641fd 100644
--- a/source/core/textures/buildtiles.cpp
+++ b/source/core/textures/buildtiles.cpp
@@ -693,11 +693,11 @@ PicAnm picanm;
 
 
 // wrappers that allow partial migration to a textureID-based setup.
-FTextureID walltype::walltexture() const
+const FTextureID walltype::walltexture() const
 {
 	return tileGetTextureID(wallpicnum);
 }
-FTextureID walltype::overtexture() const
+const FTextureID walltype::overtexture() const
 {
 	return tileGetTextureID(overpicnum);
 }
@@ -712,7 +712,7 @@ const FTextureID sectortype::floortexture() const
 	return tileGetTextureID(floorpicnum);
 }
 
-FTextureID spritetypebase::spritetexture() const
+const FTextureID spritetypebase::spritetexture() const
 {
 	return tileGetTextureID(picnum);
 }