diff --git a/src/sys/posix/posix_main.cpp b/src/sys/posix/posix_main.cpp
--- a/src/sys/posix/posix_main.cpp
+++ b/src/sys/posix/posix_main.cpp
@@ -758,7 +758,11 @@ bool Sys_LockMemory( void *ptr, int bytes ) {
 	if ( ptr == NULL || bytes <= 0 ) {
 		return false;
 	}
+#if defined( __EMSCRIPTEN__ )
+	return false;
+#else
 	return mlock( ptr, static_cast<size_t>( bytes ) ) == 0;
+#endif
 }
 
 /*
@@ -770,7 +774,11 @@ bool Sys_UnlockMemory( void *ptr, int bytes ) {
 	if ( ptr == NULL || bytes <= 0 ) {
 		return false;
 	}
+#if defined( __EMSCRIPTEN__ )
+	return false;
+#else
 	return munlock( ptr, static_cast<size_t>( bytes ) ) == 0;
+#endif
 }
 
 /*
