diff --git a/make/tex.mk b/make/tex.mk
index 73293c1a..3a1ef3ac 100644
--- a/make/tex.mk
+++ b/make/tex.mk
@@ -11,7 +11,7 @@ ifeq ($(TEX_TMPL_DIR), "")
 endif
 latex = latex
 PDFLATEX = pdflatex
-PDF_VIEWER = $(firstword $(shell which okular kpdf acroread))
+PDF_VIEWER ?= $(firstword $(shell which okular kpdf acroread))
 
 # this is what is there already
 PRE_FIG_LOCAL = $(wildcard *.fig)