diff --git a/src/input_reader.cpp b/src/input_reader.cpp
index af49f34..2fc76bd 100644
--- a/src/input_reader.cpp
+++ b/src/input_reader.cpp
@@ -108,7 +108,7 @@ const char * scalpelInputGetId (ScalpelInputReader * const reader)
     return reader->id;
 }
 
-const char scalpelInputIsOpen (ScalpelInputReader * const reader) 
+unsigned char scalpelInputIsOpen (ScalpelInputReader * const reader) 
 {
     printVerbose("scalpelInputIsOpen()\n");
     return reader->isOpen;
diff --git a/src/input_reader.h b/src/input_reader.h
index acfb4e0..cabb34b 100644
--- a/src/input_reader.h
+++ b/src/input_reader.h
@@ -79,7 +79,7 @@ int scalpelInputGetError (ScalpelInputReader * const reader);
 
 //non-abstract methods
 const char* scalpelInputGetId (ScalpelInputReader * const reader);
-const char scalpelInputIsOpen(ScalpelInputReader * const reader);
+unsigned char scalpelInputIsOpen(ScalpelInputReader * const reader);
 
 
 /********************* FILE implementation of ScalpelInputReader **********************/