diff --git a/master.cfg b/master.cfg
index 163fbff..6cea934 100644
--- a/master.cfg
+++ b/master.cfg
@@ -1049,8 +1049,8 @@ The parameters of the class are:
         if self.use_system_debuginfo:
             self.extra_conf_flags.append ('--with-separate-debug-dir=%s' % self.system_debuginfo_location)
 
-        myCFLAGS = "CFLAGS=" + default_CFLAGS + ' '.join (self.extra_CFLAGS)
-        myCXXFLAGS = "CXXFLAGS=" + default_CXXFLAGS + ' '.join (self.extra_CXXFLAGS)
+        myCFLAGS = "CFLAGS=" + default_CFLAGS + " " + ' '.join (self.extra_CFLAGS)
+        myCXXFLAGS = "CXXFLAGS=" + default_CXXFLAGS + " " + ' '.join (self.extra_CXXFLAGS)
 
         self.extra_conf_flags.append (myCFLAGS)
         self.extra_conf_flags.append (myCXXFLAGS)