diff --git a/include/mapnik/png_io.hpp b/include/mapnik/png_io.hpp
index 7f2df798a..4ea1cc53e 100644
--- a/include/mapnik/png_io.hpp
+++ b/include/mapnik/png_io.hpp
@@ -58,6 +58,7 @@ struct png_options {
     int strategy;
     int trans_mode;
     int iq_speed;
+    double iq_dither;
     double gamma;
     bool paletted;
     quantization_type quantization;
@@ -68,6 +69,7 @@ struct png_options {
         strategy(Z_DEFAULT_STRATEGY),
         trans_mode(-1),
         iq_speed(3),
+        iq_dither(-1),
         gamma(-1),
         paletted(true),
         quantization(HEXTREE),
@@ -740,6 +742,9 @@ void save_as_png8_libimagequant(T1 & file,
     liq_result *res = liq_quantize_image(attr, liq_image);
 
     // Store palettized version
+    if (opts.iq_dither != -1) {
+        liq_set_dithering_level(res, opts.iq_dither);
+    }
     image_gray8 reduced_image(width, height);
     liq_write_remapped_image(res, liq_image, (void *)reduced_image.data(), width*height*sizeof(gray8_t));
     const liq_palette *liq_pal = liq_get_palette(res);
diff --git a/src/image_util_png.cpp b/src/image_util_png.cpp
index d80ae269d..9b1f6c911 100644
--- a/src/image_util_png.cpp
+++ b/src/image_util_png.cpp
@@ -91,11 +91,18 @@ void handle_png_options(std::string const& type,
             opts.quantization = png_options::IMGQUANT;
 
         }
-        else if (boost::algorithm::starts_with(t, "iq="))
+        else if (boost::algorithm::starts_with(t, "iqs="))
         {
-            if (!mapnik::util::string2int(t.substr(3), opts.iq_speed) || opts.iq_speed < 1 || opts.iq_speed > 10)
+            if (!mapnik::util::string2int(t.substr(4), opts.iq_speed) || opts.iq_speed < 1 || opts.iq_speed > 10)
             {
-                throw ImageWriterException("invalid iq speed parameter: " + t.substr(3));
+                throw ImageWriterException("invalid iq speed parameter: " + t.substr(4));
+            }
+        }
+        else if (boost::algorithm::starts_with(t, "iqd="))
+        {
+            if (!mapnik::util::string2double(t.substr(4), opts.iq_dither) || opts.iq_dither < 0 || opts.iq_dither > 1)
+            {
+                throw ImageWriterException("invalid iq dithering parameter: " + t.substr(4));
             }
         }
         else if (t == "e=miniz")