diff --git a/FL/makefile.inc b/FL/makefile.inc
index 6e821ed..31cfeef 100644
--- a/FL/makefile.inc
+++ b/FL/makefile.inc
@@ -1,11 +1,14 @@
 # -*- mode: makefile; -*-
 
+# always regenerate source list when running under git
+FOO := $(shell [ -f .git ] && [ -x `which git` ] && rm -f FL/.sources )
+
 FL/.sources:
 	@ echo "FL_SRCS=\\" > FL/.sources
 	@ git ls-files 'FL/*.C' | tr '\n' ' ' >> FL/.sources
 	@ git ls-files 'FL/*.fl' | tr '\n' ' ' >> FL/.sources
 
-include FL/.sources
+-include FL/.sources
 
 FL_SRCS:=$(FL_SRCS:.fl=.C)
 FL_OBJS:=$(FL_SRCS:.C=.o)
diff --git a/Timeline/makefile.inc b/Timeline/makefile.inc
index 1902939..00901b5 100644
--- a/Timeline/makefile.inc
+++ b/Timeline/makefile.inc
@@ -2,12 +2,15 @@
 
 Timeline_VERSION := 0.5.0
 
+# always regenerate source list when running under git
+FOO := $(shell [ -f .git ] && [ -x `which git` ] && rm -f FL/.sources )
+
 Timeline/.sources:
 	@ echo "Timeline_SRCS=\\" > Timeline/.sources
 	@ git ls-files 'Timeline/*.C' | tr '\n' ' ' >> Timeline/.sources
 	@ git ls-files 'Timeline/*.fl' | tr '\n' ' ' >> Timeline/.sources
 
-include Timeline/.sources
+-include Timeline/.sources
 
 Timeline_SRCS += util/debug.C