diff --git a/python/frep-C.py b/python/frep-C.py
index 3a9d95a0aae7938e8099b6e02ac3e211bc244dc8..1641a3625e5f3b91178e72a774058c131aa2a085 100755
--- a/python/frep-C.py
+++ b/python/frep-C.py
@@ -135,7 +135,7 @@ int main(int argc, char** argv) {{
 	png_set_IHDR(pngfile,pnginfo,nx,ny,
 	   8,PNG_COLOR_TYPE_RGBA,PNG_INTERLACE_NONE,
 	   PNG_COMPRESSION_TYPE_BASE,PNG_FILTER_TYPE_BASE);
-   png_set_pHYs(pngfile,pnginfo,{1000*dpi/25.4},{1000*dpi/25.4},PNG_RESOLUTION_METER);
+   png_set_pHYs(pngfile,pnginfo,(png_uint_32) {1000*dpi/25.4},(png_uint_32) {1000*dpi/25.4},PNG_RESOLUTION_METER);
 	png_write_info(pngfile,pnginfo);
 	pngrow = (png_bytep) malloc(4*nx*sizeof(png_byte));
 	for (int iy = (ny-1); iy >= 0; --iy) {{
@@ -156,7 +156,8 @@ file.close()
 # compile
 #
 print("compile ...")
-os.system("time g++ frep-C.cpp -o frep-C -lm -lpng -O -ffast-math -pthread")
+#os.system("time g++ frep-C.cpp -o frep-C -lm -lpng -O -ffast-math -pthread")
+os.system("time clang++ frep-C.cpp -o frep-C -lm -lpng -O -ffast-math -pthread -Wno-bool-operation")
 #
 # execute
 #