diff --git a/CGAL_ImageIO/src/CGAL_ImageIO/gis_impl.h b/CGAL_ImageIO/src/CGAL_ImageIO/gis_impl.h
index dd69d50982e..7525c47c28e 100644
--- a/CGAL_ImageIO/src/CGAL_ImageIO/gis_impl.h
+++ b/CGAL_ImageIO/src/CGAL_ImageIO/gis_impl.h
@@ -48,7 +48,7 @@ PTRIMAGE_FORMAT createGisFormat() {
 CGAL_INLINE_FUNCTION
 int writeGis( char *name, _image* im) {
   char *outputName;
-  int res;
+  std::size_t res;
   std::size_t length, extLength = 0;
 
   length=strlen(name);
@@ -142,8 +142,8 @@ int writeGis( char *name, _image* im) {
 		if ( j<n && i<size ) sprintf( str+strlen(str), " " );
 	      }
 	      sprintf( str+strlen(str), "\n" );
-	      res = static_cast<int>(ImageIO_write( im, str, strlen( str )));
-	      if ( res  <= 0 ) {
+	      res = ImageIO_write( im, str, strlen( str ));
+	      if ( res < strlen(str) ) {
 		fprintf(stderr, "writeGis: error when writing data in \'%s\'\n", outputName);
 		if ( outputName != NULL ) ImageIO_free( outputName );
 		return( -3 );
@@ -161,8 +161,8 @@ int writeGis( char *name, _image* im) {
 		if ( j<n && i<size ) sprintf( str+strlen(str), " " );
 	      }
 	      sprintf( str+strlen(str), "\n" );
-	      res = static_cast<int>(ImageIO_write( im, str, strlen( str )));
-	      if ( res  <= 0 ) {
+	      res = ImageIO_write( im, str, strlen( str ));
+	      if ( res < strlen(str) ) {
 		fprintf(stderr, "writeGis: error when writing data in \'%s\'\n", outputName);
 		if ( outputName != NULL ) ImageIO_free( outputName );
 		return( -3 );
@@ -188,8 +188,8 @@ int writeGis( char *name, _image* im) {
 		if ( j<n && i<size ) sprintf( str+strlen(str), " " );
 	      }
 	      sprintf( str+strlen(str), "\n" );
-        res = static_cast<int>(ImageIO_write(im, str, strlen(str)));
-	      if ( res  <= 0 ) {
+              res = ImageIO_write( im, str, strlen( str ));
+	      if ( res < strlen(str) ) {
 		fprintf(stderr, "writeGis: error when writing data in \'%s\'\n", outputName);
 		if ( outputName != NULL ) ImageIO_free( outputName );
 		return( -3 );
@@ -207,8 +207,8 @@ int writeGis( char *name, _image* im) {
 		if ( j<n && i<size ) sprintf( str+strlen(str), " " );
 	      }
 	      sprintf( str+strlen(str), "\n" );
-        res = static_cast<int>(ImageIO_write(im, str, strlen(str)));
-	      if ( res  <= 0 ) {
+              res = ImageIO_write( im, str, strlen( str ));
+	      if ( res < strlen(str) ) {
 		fprintf(stderr, "writeGis: error when writing data in \'%s\'\n", outputName);
 		if ( outputName != NULL ) ImageIO_free( outputName );
 		return( -3 );
@@ -222,13 +222,14 @@ int writeGis( char *name, _image* im) {
     } /* end of switch( im->wordKind ) */
 
     ImageIO_free( str ); 
+    if (outputName != NULL) ImageIO_free(outputName);
+    return static_cast<int>(res);
   }
   else {
-    res = _writeInrimageData(im);
+    bool ret = _writeInrimageData(im);
+    if (outputName != NULL) ImageIO_free(outputName);
+    return (ret ? 1 : -1);
   }
-  if ( outputName != NULL ) ImageIO_free( outputName );
-  return res;
-  
 }
 
 CGAL_INLINE_FUNCTION
diff --git a/CGAL_ImageIO/src/CGAL_ImageIO/inr.h b/CGAL_ImageIO/src/CGAL_ImageIO/inr.h
index 5ec646040ba..8bf7aa8373e 100644
--- a/CGAL_ImageIO/src/CGAL_ImageIO/inr.h
+++ b/CGAL_ImageIO/src/CGAL_ImageIO/inr.h
@@ -36,7 +36,7 @@ int _writeInrimageHeader(const _image *im,
 
 /** Writes the given image body in an already opened file.
     @param im image descriptor */
-int _writeInrimageData(const _image *im);
+bool _writeInrimageData(const _image *im);
 
 /** read header from an opened inrimage file
     @param im opened inrmage descriptor */
diff --git a/CGAL_ImageIO/src/CGAL_ImageIO/inr_impl.h b/CGAL_ImageIO/src/CGAL_ImageIO/inr_impl.h
index 7b16dbb4788..1a212182853 100644
--- a/CGAL_ImageIO/src/CGAL_ImageIO/inr_impl.h
+++ b/CGAL_ImageIO/src/CGAL_ImageIO/inr_impl.h
@@ -194,7 +194,7 @@ int _writeInrimageHeader(const _image *im, ENDIANNESS end) {
 
 /* Writes the given image body in an already opened file.*/
 CGAL_INLINE_FUNCTION
-int _writeInrimageData(const _image *im) {
+bool _writeInrimageData(const _image *im) {
   std::size_t size, nbv, nwrt, i, v;
   unsigned char **vp;
   
@@ -204,8 +204,8 @@ int _writeInrimageData(const _image *im) {
     if(im->vectMode != VM_NON_INTERLACED) {
       size = im->xdim * im->ydim * im->zdim * im->vdim * im->wdim;
       nwrt = ImageIO_write(im, im->data, size);
-      if(nwrt != size) return -1;
-      else return 1;
+      if(nwrt != size) return false;
+      else return true;
     }
 
     /* non interlaced vectors: interlace for saving */
@@ -218,14 +218,14 @@ int _writeInrimageData(const _image *im) {
       for(i = 0; i < nbv; i++)
 	for(v = 0; v < im->vdim; v++) {
 	  if(ImageIO_write(im, (const void *) vp[v], im->wdim) != im->wdim)
-	    return -1;
+	    return false;
 	  vp[v] += im->wdim;
 	}
       ImageIO_free(vp);
-      return 1;
+      return true;
     }
   }
-  else return -1;
+  else return false;
 }
 
 
@@ -486,14 +486,13 @@ int writeInrimage(char *name,_image *im) {
     return( res );
   }
   
-  res = _writeInrimageData( im );
-  if (res < 0) {
+  if (!_writeInrimageData(im)) {
     fprintf(stderr, "writeInrimage: error: unable to write data of \'%s\'\n",
 	    name);
     ImageIO_close( im );
     im->fd = NULL;
     im->openMode = OM_CLOSE;
-    return( res );
+    return -1;
   }
 
   ImageIO_close( im );