diff --git a/packager/third_party/libpng/CMakeLists.txt b/packager/third_party/libpng/CMakeLists.txt
index 9dbc5f29c1..dd0f3ac082 100644
--- a/packager/third_party/libpng/CMakeLists.txt
+++ b/packager/third_party/libpng/CMakeLists.txt
@@ -22,9 +22,31 @@ set(SKIP_INSTALL_ALL ON)
 # A confusing name, but this means "let us tell you where to find zlib".
 set(PNG_BUILD_ZLIB ON)
 # Tell libpng where to find zlib headers.
-set(ZLIB_INCLUDE_DIR ../zlib/source/)
+set(ZLIB_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../zlib/source/")
 # Tell libpng where to find zlib library to link to.
 set(ZLIB_LIBRARY zlibstatic)
 
+# Silence these warnings:
+if(MSVC)
+  add_compile_options(
+    /wd4244
+  )
+else()
+  add_compile_options(
+    -Wno-maybe-uninitialized
+    -Wno-unused-but-set-variable
+    -Wno-unused-parameter
+    -Wno-sign-compare
+    -Wno-null-pointer-subtraction
+  )
+endif()
+
 # With these set in scope of this folder, load the library's own CMakeLists.txt.
 add_subdirectory(source)
+
+# Add missing include directories for users of png_static:
+target_include_directories(png_static PUBLIC
+  # For png.h, pngconf.h:
+  source
+  # For pnglibconf.h:
+  ${CMAKE_CURRENT_BINARY_DIR}/source)
diff --git a/packager/third_party/zlib/CMakeLists.txt b/packager/third_party/zlib/CMakeLists.txt
index 60859d6246..0e227b30b7 100644
--- a/packager/third_party/zlib/CMakeLists.txt
+++ b/packager/third_party/zlib/CMakeLists.txt
@@ -17,5 +17,12 @@ set(SKIP_INSTALL_ALL ON)
 # work, as the assembly files aren't in the repo for some reason.  So don't set
 # the AMD64 flag.
 
+# Silence these warnings:
+if(MSVC)
+  add_compile_options(/wd4244)
+else()
+  add_compile_options(-Wno-implicit-function-declaration)
+endif()
+
 # With these set in scope of this folder, load the library's own CMakeLists.txt.
 add_subdirectory(source)