diff --git a/src/mod/endpoints/mod_skypopen/Makefile.am b/src/mod/endpoints/mod_skypopen/Makefile.am
index 1b59c8a3c3..aab3d25adf 100644
--- a/src/mod/endpoints/mod_skypopen/Makefile.am
+++ b/src/mod/endpoints/mod_skypopen/Makefile.am
@@ -16,7 +16,7 @@ mod_skypopen_la_LIBADD   = $(switch_builddir)/libfreeswitch.la $(SPANDSP_LA) $(T
 mod_skypopen_la_LDFLAGS  = -avoid-version -module -no-undefined -shared -lX11
 
 $(SPANDSP_LA): $(TIFF_LA) $(SPANDSP_DIR) $(SPANDSP_DIR)/.update
-	cd $(SPANDSP_BUILDDIR) && $(MAKE) -j1
+	cd $(SPANDSP_BUILDDIR) && $(MAKE) -j1 CFLAGS="$(CFLAGS) -I$(TIFF_BUILDDIR)/libtiff -I$(TIFF_DIR)/libtiff"
 	$(TOUCH_TARGET)
 
 $(TIFF_LA): $(TIFF_DIR) $(TIFF_DIR)/.update