diff --git a/src/dsp/dsp.h b/src/dsp/dsp.h
index 813fed4a..ccb9df7b 100644
--- a/src/dsp/dsp.h
+++ b/src/dsp/dsp.h
@@ -42,6 +42,9 @@ extern "C" {
 # define __has_builtin(x) 0
 #endif
 
+// for now, none of the optimizations below are available in emscripten
+#if !defined(EMSCRIPTEN)
+
 #if defined(_MSC_VER) && _MSC_VER > 1310 && \
     (defined(_M_X64) || defined(_M_IX86))
 #define WEBP_MSC_SSE2  // Visual C++ SSE2 targets
@@ -100,6 +103,8 @@ extern "C" {
 #define WEBP_USE_MSA
 #endif
 
+#endif  /* EMSCRIPTEN */
+
 // This macro prevents thread_sanitizer from reporting known concurrent writes.
 #define WEBP_TSAN_IGNORE_FUNCTION
 #if defined(__has_feature)