diff --git a/msvcc.sh b/msvcc.sh
index 7440deb3..92080762 100755
--- a/msvcc.sh
+++ b/msvcc.sh
@@ -105,9 +105,13 @@ do
       shift 1
     ;;
     -DFFI_DEBUG)
-      # Link against debug CRT and enable runtime error checks.
+      # Enable runtime error checks.
       args="$args -RTC1"
       defines="$defines $1"
+      shift 1
+    ;;
+    -DUSE_DEBUG_RTL)
+      # Link against debug CRT.
       md=-MDd
       shift 1
     ;;