diff --git a/src/Makefile.in b/src/Makefile.in
index 910e2e854a6c0478a54eebf5ba2a3c010fc73a70..70218b6338688e8498b486cb92993499c5a5e44e 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -48,7 +48,7 @@ OPTIMIZE=@OPTIMIZE@
 
 # Preprocessor flags.
 PREFLAGS=-I. -I$(SRCDIR) $(DEFINES)
-OTHERFLAGS=@CFLAGS@ $(OSFLAGS) $(OPTIMIZE) $(WARN) $(PROFIL)
+OTHERFLAGS=@CFLAGS@ @CPPFLAGS@ $(OSFLAGS) $(OPTIMIZE) $(WARN) $(PROFIL)
 CFLAGS=$(PREFLAGS) $(OTHERFLAGS)
 
 CC=@CC@