diff --git a/splash/SplashBitmap.cc b/splash/SplashBitmap.cc
index 5fe61a2..c3ed380 100644
--- a/splash/SplashBitmap.cc
+++ b/splash/SplashBitmap.cc
@@ -162,7 +162,7 @@ SplashBitmap::~SplashBitmap() {
 }
 
 
-SplashError SplashBitmap::writePNMFile(char *fileName) {
+SplashError SplashBitmap::writePNMFile(const char *fileName) {
   FILE *f;
   SplashError e;
 
@@ -257,7 +257,7 @@ SplashError SplashBitmap::writePNMFile(FILE *f) {
   return splashOk;
 }
 
-SplashError SplashBitmap::writeAlphaPGMFile(char *fileName) {
+SplashError SplashBitmap::writeAlphaPGMFile(const char *fileName) {
   FILE *f;
 
   if (!alpha) {
@@ -335,7 +335,7 @@ SplashColorPtr SplashBitmap::takeData() {
   return data2;
 }
 
-SplashError SplashBitmap::writeImgFile(SplashImageFileFormat format, char *fileName, int hDPI, int vDPI, const char *compressionString) {
+SplashError SplashBitmap::writeImgFile(SplashImageFileFormat format, const char *fileName, int hDPI, int vDPI, const char *compressionString) {
   FILE *f;
   SplashError e;
 
diff --git a/splash/SplashBitmap.h b/splash/SplashBitmap.h
index 0bff205..05ad16e 100644
--- a/splash/SplashBitmap.h
+++ b/splash/SplashBitmap.h
@@ -67,11 +67,11 @@ public:
   Guchar *getAlphaPtr() { return alpha; }
   GooList *getSeparationList() { return separationList; }
 
-  SplashError writePNMFile(char *fileName);
+  SplashError writePNMFile(const char *fileName);
   SplashError writePNMFile(FILE *f);
-  SplashError writeAlphaPGMFile(char *fileName);
+  SplashError writeAlphaPGMFile(const char *fileName);
   
-  SplashError writeImgFile(SplashImageFileFormat format, char *fileName, int hDPI, int vDPI, const char *compressionString = "");
+  SplashError writeImgFile(SplashImageFileFormat format, const char *fileName, int hDPI, int vDPI, const char *compressionString = "");
   SplashError writeImgFile(SplashImageFileFormat format, FILE *f, int hDPI, int vDPI, const char *compressionString = "");
   SplashError writeImgFile(ImgWriter *writer, FILE *f, int hDPI, int vDPI);