diff --git a/CMakeLists.txt b/CMakeLists.txt
index ec2850b0..b785a8e6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -665,6 +665,21 @@ if(WEBP_BUILD_EXTRAS)
                         ${CMAKE_CURRENT_BINARY_DIR}/src ${SDL2_INCLUDE_DIRS})
     set(WEBP_HAVE_SDL 1)
     target_compile_definitions(vwebp_sdl PUBLIC WEBP_HAVE_SDL)
+
+    set(CMAKE_REQUIRED_INCLUDES "${SDL2_INCLUDE_DIRS}")
+    check_c_source_compiles(
+      "
+        #define SDL_MAIN_HANDLED
+        #include \"SDL.h\"
+        int main(void) {
+          return 0;
+        }
+      "
+      HAVE_JUST_SDL_H)
+    set(CMAKE_REQUIRED_INCLUDES)
+    if(HAVE_JUST_SDL_H)
+      target_compile_definitions(vwebp_sdl PRIVATE WEBP_HAVE_JUST_SDL_H)
+    endif()
   endif()
 endif()
 
@@ -679,13 +694,10 @@ if(WEBP_BUILD_WEBP_JS)
   else()
     set(emscripten_stack_size "-sTOTAL_STACK=5MB")
   endif()
-  # Set SDL2 flags so that ports are downloaded by emscripten.
-  set(EMSCRIPTEN_SDL2_FLAGS "-sUSE_SDL=2 -sUSE_SDL_IMAGE=2")
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${EMSCRIPTEN_SDL2_FLAGS}")
+  find_package(SDL2 REQUIRED)
   # wasm2js does not support SIMD.
   if(NOT WEBP_ENABLE_SIMD)
     # JavaScript version
-    find_package(SDL2 QUIET)
     add_executable(webp_js ${CMAKE_CURRENT_SOURCE_DIR}/extras/webp_to_sdl.c)
     target_link_libraries(webp_js webpdecoder SDL2)
     target_include_directories(webp_js PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
@@ -693,10 +705,13 @@ if(WEBP_BUILD_WEBP_JS)
     set_target_properties(
       webp_js
       PROPERTIES
+        # Emscripten puts -sUSE_SDL2=1 in this variable, though it's needed at
+        # compile time to ensure the headers are downloaded.
+        COMPILE_OPTIONS "${SDL2_LIBRARIES}"
         LINK_FLAGS
         "-sWASM=0 ${emscripten_stack_size} \
          -sEXPORTED_FUNCTIONS=_WebPToSDL -sINVOKE_RUN=0 \
-         -sEXPORTED_RUNTIME_METHODS=cwrap ${EMSCRIPTEN_SDL2_FLAGS} \
+         -sEXPORTED_RUNTIME_METHODS=cwrap ${SDL2_LIBRARIES} \
          -sALLOW_MEMORY_GROWTH")
     set_target_properties(webp_js PROPERTIES OUTPUT_NAME webp)
     target_compile_definitions(webp_js PUBLIC EMSCRIPTEN WEBP_HAVE_SDL)
@@ -709,10 +724,13 @@ if(WEBP_BUILD_WEBP_JS)
   set_target_properties(
     webp_wasm
     PROPERTIES
+      # Emscripten puts -sUSE_SDL2=1 in this variable, though it's needed at
+      # compile time to ensure the headers are downloaded.
+      COMPILE_OPTIONS "${SDL2_LIBRARIES}"
       LINK_FLAGS
       "-sWASM=1 ${emscripten_stack_size} \
        -sEXPORTED_FUNCTIONS=_WebPToSDL -sINVOKE_RUN=0 \
-       -sEXPORTED_RUNTIME_METHODS=cwrap ${EMSCRIPTEN_SDL2_FLAGS} \
+       -sEXPORTED_RUNTIME_METHODS=cwrap ${SDL2_LIBRARIES} \
        -sALLOW_MEMORY_GROWTH")
   target_compile_definitions(webp_wasm PUBLIC EMSCRIPTEN WEBP_HAVE_SDL)
 
diff --git a/webp_js/index.html b/webp_js/index.html
index 33cacb4c..e7c3b652 100644
--- a/webp_js/index.html
+++ b/webp_js/index.html
@@ -29,6 +29,8 @@ function decode(webp_data, canvas_id) {
   // clear previous picture (if any)
   Module.canvas = canvas;
   canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
+  // Map this canvas to the default selector used by emscripten/SDL2.
+  specialHTMLTargets["#canvas"] = Module.canvas;
   // decode and measure timing
   var start = new Date();
   var ret = WebpToCanvas(webp_data, webp_data.length);
diff --git a/webp_js/index_wasm.html b/webp_js/index_wasm.html
index 7a9b362a..29933aba 100644
--- a/webp_js/index_wasm.html
+++ b/webp_js/index_wasm.html
@@ -30,6 +30,8 @@ function decode(webp_data, canvas_id) {
   // clear previous picture (if any)
   Module.canvas = canvas;
   canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
+  // Map this canvas to the default selector used by emscripten/SDL2.
+  specialHTMLTargets["#canvas"] = Module.canvas;
   // decode and measure timing
   var start = new Date();
   var ret = WebpToCanvas(webp_data, webp_data.length);