diff --git a/tools/web.py b/tools/web.py
index 8953325c..08aac635 100644
--- a/tools/web.py
+++ b/tools/web.py
@@ -39,8 +39,8 @@ def generate(env):
         env.Append(LINKFLAGS=["-s", "USE_PTHREADS=1"])
 
     # Build as side module (shared library).
-    env.Append(CPPFLAGS=["-s", "SIDE_MODULE=1"])
-    env.Append(LINKFLAGS=["-s", "SIDE_MODULE=1"])
+    env.Append(CCFLAGS=["-sSIDE_MODULE=1"])
+    env.Append(LINKFLAGS=["-sSIDE_MODULE=1"])
 
     env.Append(CPPDEFINES=["WEB_ENABLED", "UNIX_ENABLED"])