diff --git a/common/file.cpp b/common/file.cpp
index dd12361498c..7f81cdddf14 100644
--- a/common/file.cpp
+++ b/common/file.cpp
@@ -188,11 +188,11 @@ void File::close() {
 	_handle = NULL;
 }
 
-bool File::isOpen() {
+bool File::isOpen() const {
 	return _handle != NULL;
 }
 
-bool File::ioFailed() {
+bool File::ioFailed() const {
 	return _ioFailed != 0;
 }
 
diff --git a/common/file.h b/common/file.h
index ff6e18f1834..6bf281ff924 100644
--- a/common/file.h
+++ b/common/file.h
@@ -51,8 +51,8 @@ public:
 	bool open(const char *filename, const Common::String &directory) { return open(filename, directory.c_str()); }
 	bool open(const char *filename, const char *directory = NULL, int mode = kFileReadMode, byte encbyte = 0);
 	void close();
-	bool isOpen();
-	bool ioFailed();
+	bool isOpen() const;
+	bool ioFailed() const;
 	void clearIOFailed();
 	bool eof();
 	uint32 pos();