diff --git a/SConstruct b/SConstruct
index 00fb95da6..e009d2542 100644
--- a/SConstruct
+++ b/SConstruct
@@ -985,13 +985,18 @@ if not preconfigured:
             common_cxx_flags = '-D%s ' % env['PLATFORM'].upper()
 
         
-        svn_version = call('svnversion')
-        if not svn_version == 'exported':
-            pattern = r'(\d+)(.*)'
-            try:
-                rev = re.match(pattern,svn_version).groups()[0]
-                common_cxx_flags += '-DSVN_REVISION=%s ' % rev
-            except: pass
+        
+        if not env['FAST']:
+            # if we are in SCons FAST mode then make to 
+            # to avoid unnessary re-compiles due to changing
+            # CFLAGS when revision number increases 
+            svn_version = call('svnversion')
+            if not svn_version == 'exported':
+                pattern = r'(\d+)(.*)'
+                try:
+                    rev = re.match(pattern,svn_version).groups()[0]
+                    common_cxx_flags += '-DSVN_REVISION=%s ' % rev
+                except: pass
             
         # Mac OSX (Darwin) special settings
         if env['PLATFORM'] == 'Darwin':