diff --git a/Makefile.am b/Makefile.am
index fa75c366a737458e6dfb198ab669b51253da5cbd..f621563139cb6359a8a4e19f0728147613f8e1b8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -35,7 +35,7 @@ EXTRA_DIST = \
  doc/opus_logo.svg
 
 # Targets to build and install just the library without the docs
-opusfile install-opusfile: export NO_DOXYGEN = 1
+opusfile install-opusfile: NO_DOXYGEN = 1
 
 opusfile: all
 install-opusfile: install