diff --git a/src/Image.cc b/src/Image.cc
index 06dd564ae..a93446713 100644
--- a/src/Image.cc
+++ b/src/Image.cc
@@ -956,7 +956,7 @@ Image::decodeJPEGBufferIntoMimeSurface(uint8_t *buf, unsigned len) {
 
   jpeg_mem_src(&args, buf, len);
 
-  jpeg_read_header(&args, 1);
+  jpeg_read_header(&args, (boolean)1);
   jpeg_start_decompress(&args);
   width = naturalWidth = args.output_width;
   height = naturalHeight = args.output_height;
@@ -1080,7 +1080,7 @@ Image::loadJPEGFromBuffer(uint8_t *buf, unsigned len) {
 
   jpeg_mem_src(&args, buf, len);
 
-  jpeg_read_header(&args, 1);
+  jpeg_read_header(&args, (boolean)1);
   jpeg_start_decompress(&args);
   width = naturalWidth = args.output_width;
   height = naturalHeight = args.output_height;
@@ -1129,7 +1129,7 @@ Image::loadJPEG(FILE *stream) {
 
     jpeg_stdio_src(&args, stream);
 
-    jpeg_read_header(&args, 1);
+    jpeg_read_header(&args, (boolean)1);
     jpeg_start_decompress(&args);
 
     if (args.output_width > canvas_max_side || args.output_height > canvas_max_side) {
diff --git a/src/JPEGStream.h b/src/JPEGStream.h
index 43c74f139..780d0d1b2 100644
--- a/src/JPEGStream.h
+++ b/src/JPEGStream.h
@@ -36,7 +36,7 @@ empty_closure_output_buffer(j_compress_ptr cinfo){
   dest->buffer = (JOCTET *)malloc(dest->bufsize);
   cinfo->dest->next_output_byte = dest->buffer;
   cinfo->dest->free_in_buffer = dest->bufsize;
-  return true;
+  return (boolean)true;
 }
 
 void
@@ -93,12 +93,12 @@ void encode_jpeg(jpeg_compress_struct cinfo, cairo_surface_t *surface, int quali
   jpeg_set_defaults(&cinfo);
   if (progressive)
     jpeg_simple_progression(&cinfo);
-  jpeg_set_quality(&cinfo, quality, (quality < 25) ? 0 : 1);
+  jpeg_set_quality(&cinfo, quality, (boolean)((quality < 25) ? 0 : 1));
   cinfo.comp_info[0].h_samp_factor = chromaHSampFactor;
   cinfo.comp_info[0].v_samp_factor = chromaVSampFactor;
 
   JSAMPROW slr;
-  jpeg_start_compress(&cinfo, TRUE);
+  jpeg_start_compress(&cinfo, (boolean)TRUE);
   unsigned char *dst;
   unsigned int *src = (unsigned int *)cairo_image_surface_get_data(surface);
   int sl = 0;