diff --git a/otk/Makefile.am b/otk/Makefile.am
index 7d020cc6..2ee73c10 100644
--- a/otk/Makefile.am
+++ b/otk/Makefile.am
@@ -1,4 +1,7 @@
-CXXFLAGS=$(XFT_CFLAGS) $(PYTHON_CFLAGS) @CXXFLAGS@
+buttonsdir = $(pkgdatadir)/buttons
+
+CXXFLAGS=$(XFT_CFLAGS) $(PYTHON_CFLAGS) @CXXFLAGS@ \
+-DBUTTONSDIR=\"$(buttonsdir)\"
 
 INCLUDES= -I../src