diff --git a/libs/freetdm/configure.ac b/libs/freetdm/configure.ac
index a69618ba6f..f59cab95d6 100644
--- a/libs/freetdm/configure.ac
+++ b/libs/freetdm/configure.ac
@@ -54,7 +54,7 @@ fi
 
 AC_SUBST([confdir])
 
-DEFAULT_INCLUDES="-I. -I./src/include -I$(srcdir)"
+DEFAULT_INCLUDES="-I. -I./src/include -I\$(srcdir)"
 AC_SUBST([DEFAULT_INCLUDES])
 
 # Where to install the modules