diff --git a/Makefile b/Makefile
index 10a8078bb4..3b25f1fb04 100644
--- a/Makefile
+++ b/Makefile
@@ -57,7 +57,8 @@ MAVEN_VERSION:=$(VNUM)-SNAPSHOT
 
 JARNAME:=vassal-app-$(MAVEN_VERSION)
 
-GITBRANCH:=$(shell git rev-parse --abbrev-ref HEAD)
+#Slashes are substituted so as not to create subdirectories
+GITBRANCH := $(subst /,_,$(shell git rev-parse --abbrev-ref HEAD))
 GITCOMMIT:=$(shell git rev-parse --short HEAD)
 
 ifeq ($(shell git describe --tags), $(MAVEN_VERSION))