diff --git a/video/subtitles.cpp b/video/subtitles.cpp
index 91007387974..19b12075891 100644
--- a/video/subtitles.cpp
+++ b/video/subtitles.cpp
@@ -216,7 +216,7 @@ bool SRTParser::parseFile(const char *fname) {
 	return true;
 }
 
-Common::String SRTParser::getSubtitle(uint32 timestamp) {
+Common::String SRTParser::getSubtitle(uint32 timestamp) const {
 	SRTEntry test(0, timestamp, 0, "");
 	SRTEntry *testptr = &test;
 
@@ -299,7 +299,7 @@ void Subtitles::setPadding(uint16 horizontal, uint16 vertical) {
 	_vPad = vertical;
 }
 
-bool Subtitles::drawSubtitle(uint32 timestamp, bool force) {
+bool Subtitles::drawSubtitle(uint32 timestamp, bool force) const {
 	Common::String subtitle;
 	if (_loaded) {
 		subtitle = _srtParser.getSubtitle(timestamp);
@@ -375,7 +375,7 @@ bool Subtitles::drawSubtitle(uint32 timestamp, bool force) {
 	return true;
 }
 
-void Subtitles::renderSubtitle() {
+void Subtitles::renderSubtitle() const {
 	_surface->fillRect(Common::Rect(0, 0, _surface->w, _surface->h), _transparentColor);
 
 	Common::Array<Common::U32String> lines;
diff --git a/video/subtitles.h b/video/subtitles.h
index f649921567b..0060e610fd1 100644
--- a/video/subtitles.h
+++ b/video/subtitles.h
@@ -52,7 +52,7 @@ public:
 
 	void cleanup();
 	bool parseFile(const char *fname);
-	Common::String getSubtitle(uint32 timestamp);
+	Common::String getSubtitle(uint32 timestamp) const;
 
 private:
 	Common::Array<SRTEntry *> _entries;
@@ -69,11 +69,11 @@ public:
 	void setBBox(const Common::Rect bbox);
 	void setColor(byte r, byte g, byte b);
 	void setPadding(uint16 horizontal, uint16 vertical);
-	bool drawSubtitle(uint32 timestamp, bool force = false);
+	bool drawSubtitle(uint32 timestamp, bool force = false) const;
 	bool isLoaded() const { return _loaded || _subtitleDev; }
 
 private:
-	void renderSubtitle();
+	void renderSubtitle() const;
 
 	SRTParser _srtParser;
 	bool _loaded;
@@ -85,13 +85,13 @@ private:
 
 	Graphics::Surface *_surface;
 
-	Common::Rect _drawRect;
+	mutable Common::Rect _drawRect;
 	Common::Rect _requestedBBox;
-	Common::Rect _realBBox;
-	int16 _lastOverlayWidth, _lastOverlayHeight;
+	mutable Common::Rect _realBBox;
+	mutable int16 _lastOverlayWidth, _lastOverlayHeight;
 
 	Common::String _fname;
-	Common::String _subtitle;
+	mutable Common::String _subtitle;
 	uint32 _color;
 	uint32 _blackColor;
 	uint32 _transparentColor;