diff --git a/acprep b/acprep
index fd7f5249..32ca177a 100755
--- a/acprep
+++ b/acprep
@@ -811,7 +811,7 @@ class PrepareBuild(CommandLineApp):
                     'CXXFLAGS', 'LDFLAGS', 'LDARCHFLAGS'):
             value = self.__dict__[var]
             if value:
-                first = True
+                first = not self.envvars[var]
                 for member in value:
                     #escaped = self.escape_string(member)
                     #if member != escaped: