diff --git a/configure.in b/configure.in
index 19068609..bef1b8e2 100644
--- a/configure.in
+++ b/configure.in
@@ -53,9 +53,12 @@ fi
 
 CFLAGS='-I./include -I $(top_srcdir)/include -Wall -W'
 if test x$debug = xtrue; then
-  CFLAGS="$CFLAGS  -g -O0 -DDEBUG"
+	CFLAGS="$CFLAGS -g -O0 -DDEBUG"
 else
-  CFLAGS="$CFLAGS -O3 -fomit-frame-pointer -funroll-loops -ffast-math -finline-functions -DNDEBUG"
+	CFLAGS="$CFLAGS -O3 -DNDEBUG"
+		if test x$GCC = xyes; then
+			CFLAGS="$CFLAGS -fomit-frame-pointer -funroll-loops -ffast-math -finline-functions"
+		fi
 fi
 
 AC_OUTPUT(	Makefile	\