diff --git a/tools/configure b/tools/configure
index c06611e105..3d1aad7667 100755
--- a/tools/configure
+++ b/tools/configure
@@ -3627,7 +3627,7 @@ if [ -n "$ARG_LCDWIDTH" ]; then
 fi
 
 # remove parts from the cmdline we're going to set unconditionally
-cmdline=`echo $cmdline | sed -e s,--target=[a-zA-Z0-9]\*,,g \
+cmdline=`echo $cmdline | sed -e s,--target=[a-zA-Z_0-9]\*,,g \
                             -e s,--ram=[0-9]\*,,g \
                             -e s,--rbdir=[./a-zA-Z0-9]\*,,g \
                             -e s,--type=[a-zA-Z]\*,,g`