diff --git a/configure.ac b/configure.ac
index 923adfe1..24a7ea68 100644
--- a/configure.ac
+++ b/configure.ac
@@ -644,6 +644,9 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #ifndef NATIVE_LITTLE_ENDIAN
 # error libsodium currently expects a little endian CPU for the 128-bit type
 #endif
+#ifdef __EMSCRIPTEN__
+# error emscripten currently doesn't support some operations on integers larger than 64 bits
+#endif
 #include <stddef.h>
 #include <stdint.h>
 #if defined(__SIZEOF_INT128__)