diff --git a/include/mbgl/util/image.hpp b/include/mbgl/util/image.hpp
index b2f70e144..91a451890 100644
--- a/include/mbgl/util/image.hpp
+++ b/include/mbgl/util/image.hpp
@@ -7,7 +7,7 @@
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, void *rgba);
+std::string compress_png(int width, int height, const void *rgba);
 
 
 class Image {
diff --git a/platform/darwin/image.mm b/platform/darwin/image.mm
index f6a8a6783..31373e9d1 100644
--- a/platform/darwin/image.mm
+++ b/platform/darwin/image.mm
@@ -11,7 +11,7 @@
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, void *rgba) {
+std::string compress_png(int width, int height, const void *rgba) {
     CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, rgba, width * height * 4, NULL);
     if (!provider) {
         return "";
diff --git a/platform/default/image.cpp b/platform/default/image.cpp
index 12aea898c..d7dcfc38b 100644
--- a/platform/default/image.cpp
+++ b/platform/default/image.cpp
@@ -27,7 +27,7 @@ const static bool png_version_check = []() {
 namespace mbgl {
 namespace util {
 
-std::string compress_png(int width, int height, void *rgba) {
+std::string compress_png(int width, int height, const void *rgba) {
     png_voidp error_ptr = 0;
     png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, NULL, NULL);
     if (!png_ptr) {