diff --git a/addons/ot/Makefile b/addons/ot/Makefile
index ef48ce4..0cc8c6a 100644
--- a/addons/ot/Makefile
+++ b/addons/ot/Makefile
@@ -3,6 +3,7 @@
 # OT_INC     : force the include path to libopentracing-c-wrapper
 # OT_LIB     : force the lib path to libopentracing-c-wrapper
 # OT_RUNPATH : add libopentracing-c-wrapper RUNPATH to haproxy executable
+# OT_USE_VARS : allows the use of variables for the OpenTracing context
 
 OT_DEFINE    =
 OT_CFLAGS    =
@@ -61,8 +62,13 @@
 	addons/ot/src/parser.o      \
 	addons/ot/src/pool.o        \
 	addons/ot/src/scope.o       \
-	addons/ot/src/util.o        \
+	addons/ot/src/util.o
+
+ifneq ($(OT_USE_VARS),)
+OT_DEFINE     = -DUSE_OT_VARS
+OPTIONS_OBJS += \
 	addons/ot/src/vars.o
+endif
 
 OPTIONS_CFLAGS  += $(OT_CFLAGS) -Iaddons/ot/include
 OPTIONS_LDFLAGS += $(OT_LDFLAGS)