diff --git a/SConstruct b/SConstruct
index 99951efea..55c5df95a 100644
--- a/SConstruct
+++ b/SConstruct
@@ -251,7 +251,7 @@ pickle_store = [# Scons internal variables
         'PYTHON_INSTALL_LOCATION',
         'PYTHON_SYS_PREFIX',
         'COLOR_PRINT',
-        'BOOST_SYSTEM_REQUIRED',
+        'HAS_BOOST_SYSTEM',
         ]
 
 # Add all other user configurable options to pickle pickle_store
@@ -304,6 +304,13 @@ if not force_configure:
     else:
         preconfigured = False
 
+# check for missing keys in pickled settings
+# which can occur when keys are added or changed between
+# rebuilds, e.g. for folks following trunk
+for opt in pickle_store:
+    if not opt in env:
+        preconfigured = False
+
 # if custom arguments are supplied make sure to accept them
 if opts.args:
     # since we have custom arguments update environment with all opts to 
@@ -731,22 +738,21 @@ if not preconfigured:
         
     conf.FindBoost(BOOST_SEARCH_PREFIXES,thread_flag)
     
-    # get boost version from boost headers rather than previous approach
-    # of fetching from the user provided INCLUDE path
-    boost_system_required = False
+    # boost system is used in boost 1.35 and greater
+    has_boost_system = False
     boost_lib_version_from_header = conf.GetBoostLibVersion()
     if boost_lib_version_from_header:
         boost_version_from_header = int(boost_lib_version_from_header.split('_')[1])
-        if boost_version_from_header >= 35 and env['PLATFORM'] == 'Darwin':
-            boost_system_required = True
-            env['BOOST_SYSTEM_REQUIRED'] = True
+        if boost_version_from_header >= 35:
+            has_boost_system = True
+            env['HAS_BOOST_SYSTEM'] = True
         else:
-            boost_system_required = False
-            env['BOOST_SYSTEM_REQUIRED'] = False
+            has_boost_system = False
+            env['HAS_BOOST_SYSTEM'] = False
     
     # The other required boost headers.
     BOOST_LIBSHEADERS = [
-        ['system', 'boost/system/system_error.hpp', boost_system_required],
+        ['system', 'boost/system/system_error.hpp', has_boost_system],
         ['filesystem', 'boost/filesystem/operations.hpp', True],
         ['regex', 'boost/regex.hpp', True],
         ['iostreams','boost/iostreams/device/mapped_file.hpp',True],
diff --git a/plugins/input/ogr/SConscript b/plugins/input/ogr/SConscript
index c73277b12..8eddd9907 100644
--- a/plugins/input/ogr/SConscript
+++ b/plugins/input/ogr/SConscript
@@ -36,7 +36,7 @@ ogr_src = Split(
 libraries = [env['PLUGINS']['ogr']['lib']]
 
 if env['PLATFORM'] == 'Darwin':
-    if env['BOOST_SYSTEM_REQUIRED']:
+    if env['HAS_BOOST_SYSTEM']:
         boost_system = 'boost_system%s' % env['BOOST_APPEND']
         libraries.append(boost_system)
     libraries.append('mapnik')
diff --git a/src/SConscript b/src/SConscript
index 47dde1bb1..98bf8019d 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -49,7 +49,7 @@ if env['THREADING'] == 'multi':
     libraries.append('boost_thread%s' % env['BOOST_APPEND'])
         
 if env['PLATFORM'] == 'Darwin':
-    if env['BOOST_SYSTEM_REQUIRED']:
+    if env['HAS_BOOST_SYSTEM']:
         libraries.append('boost_system%s' % env['BOOST_APPEND'])
     
 if env['INTERNAL_LIBAGG']:
diff --git a/utils/ogrindex/SConscript b/utils/ogrindex/SConscript
index 5118ac0d0..c209f7994 100644
--- a/utils/ogrindex/SConscript
+++ b/utils/ogrindex/SConscript
@@ -40,7 +40,7 @@ boost_filesystem = 'boost_filesystem%s' % env['BOOST_APPEND']
 libraries =  [boost_program_options,boost_iostreams,boost_filesystem,env['PLUGINS']['ogr']['lib'],'mapnik']
 
 if env['PLATFORM'] == 'Darwin':
-    if env['BOOST_SYSTEM_REQUIRED']:
+    if env['HAS_BOOST_SYSTEM']:
         boost_system = 'boost_system%s' % env['BOOST_APPEND']
         libraries.append(boost_system)
     libraries.append(env['ICU_LIB_NAME'])
diff --git a/utils/shapeindex/SConscript b/utils/shapeindex/SConscript
index f97afab9e..30509c330 100644
--- a/utils/shapeindex/SConscript
+++ b/utils/shapeindex/SConscript
@@ -43,10 +43,7 @@ libraries =  [boost_program_options,boost_iostreams,boost_filesystem]
 
 boost_system = 'boost_system%s' % env['BOOST_APPEND']
 
-if env['SUNCC']:
-    libraries.append(boost_system)
-
-if env['PLATFORM'] == 'Darwin' and env['BOOST_SYSTEM_REQUIRED']:
+if env['HAS_BOOST_SYSTEM']:
     libraries.append(boost_system)