diff --git a/SConstruct b/SConstruct
index cf6d46855c9..f3331f3b0d8 100644
--- a/SConstruct
+++ b/SConstruct
@@ -700,12 +700,11 @@ if env.msvc:
     else:
         env.Append(LINKFLAGS=["/DEBUG:NONE"])
 
-    if env["optimize"] == "speed":
+    if env["optimize"].startswith("speed"):
         env.Append(CCFLAGS=["/O2"])
         env.Append(LINKFLAGS=["/OPT:REF"])
-    elif env["optimize"] == "speed_trace":
-        env.Append(CCFLAGS=["/O2"])
-        env.Append(LINKFLAGS=["/OPT:REF", "/OPT:NOICF"])
+        if env["optimize"] == "speed_trace":
+            env.Append(LINKFLAGS=["/OPT:NOICF"])
     elif env["optimize"] == "size":
         env.Append(CCFLAGS=["/O1"])
         env.Append(LINKFLAGS=["/OPT:REF"])
@@ -737,17 +736,25 @@ else:
         else:
             env.Append(LINKFLAGS=["-s"])
 
+    # Linker needs optimization flags too, at least for Emscripten.
+    # For other toolchains, this _may_ be useful for LTO too to disambiguate.
+
     if env["optimize"] == "speed":
         env.Append(CCFLAGS=["-O3"])
+        env.Append(LINKFLAGS=["-O3"])
     # `-O2` is friendlier to debuggers than `-O3`, leading to better crash backtraces.
     elif env["optimize"] == "speed_trace":
         env.Append(CCFLAGS=["-O2"])
+        env.Append(LINKFLAGS=["-O2"])
     elif env["optimize"] == "size":
         env.Append(CCFLAGS=["-Os"])
+        env.Append(LINKFLAGS=["-Os"])
     elif env["optimize"] == "debug":
         env.Append(CCFLAGS=["-Og"])
+        env.Append(LINKFLAGS=["-Og"])
     elif env["optimize"] == "none":
         env.Append(CCFLAGS=["-O0"])
+        env.Append(LINKFLAGS=["-O0"])
 
 # Needs to happen after configure to handle "auto".
 if env["lto"] != "none":