diff --git a/bootstrap b/bootstrap
index 3be3d1f68bc085034e7006f483b2d7ff2c16101c..7b044e72bb2e32eba7f51d557f417b367eedbfee 100755
--- a/bootstrap
+++ b/bootstrap
@@ -460,6 +460,12 @@ cmake_escape ()
   echo $1 | sed "s/ /\\\\ /g"
 }
 
+# Strip prefix from argument
+cmake_arg ()
+{
+  echo "$1" | sed "s/^${2-[^=]*=}//"
+}
+
 # Write message to the log
 cmake_log ()
 {
@@ -544,21 +550,24 @@ cmake_ccache_enabled=
 cmake_prefix_dir="${cmake_default_prefix}"
 while test $# != 0; do
   case "$1" in
-  --prefix=*) cmake_prefix_dir=`cmake_fix_slashes "${1#*=}"` ;;
-  --parallel=*) cmake_parallel_make="${1#*=}" ;;
-  --datadir=*) cmake_data_dir="${1#*=}" ;;
-  --docdir=*) cmake_doc_dir="${1#*=}" ;;
-  --mandir=*) cmake_man_dir="${1#*=}" ;;
-  --init=*) cmake_init_file="${1#*=}" ;;
+  --prefix=*) dir=`cmake_arg "$1"`
+              cmake_prefix_dir=`cmake_fix_slashes "$dir"` ;;
+  --parallel=*) cmake_parallel_make=`cmake_arg "$1"` ;;
+  --datadir=*) cmake_data_dir=`cmake_arg "$1"` ;;
+  --docdir=*) cmake_doc_dir=`cmake_arg "$1"` ;;
+  --mandir=*) cmake_man_dir=`cmake_arg "$1"` ;;
+  --init=*) cmake_init_file=`cmake_arg "$1"` ;;
   --system-libs) cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARIES=1" ;;
   --no-system-libs) cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARIES=0" ;;
   --system-bzip2|--system-curl|--system-expat|--system-libarchive|--system-zlib)
-    cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARY_`cmake_toupper ${1#--system-}`=1" ;;
+    lib=`cmake_arg "$1" "--system-"`
+    cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARY_`cmake_toupper $lib`=1" ;;
   --no-system-bzip2|--no-system-curl|--no-system-expat|--no-system-libarchive|--no-system-zlib)
-    cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARY_`cmake_toupper ${1#--no-system-}`=0" ;;
+    lib=`cmake_arg "$1" "--no-system-"`
+    cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARY_`cmake_toupper $lib`=0" ;;
   --qt-gui) cmake_bootstrap_qt_gui="1" ;;
   --no-qt-gui) cmake_bootstrap_qt_gui="0" ;;
-  --qt-qmake=*) cmake_bootstrap_qt_qmake="${1#*=}" ;;
+  --qt-qmake=*) cmake_bootstrap_qt_qmake=`cmake_arg "$1"` ;;
   --help) cmake_usage ;;
   --version) cmake_version_display ; exit 2 ;;
   --verbose) cmake_verbose=TRUE ;;