diff --git a/Makefile.am b/Makefile.am
index c226113cc..beea69d95 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -21,6 +21,13 @@ bin_SCRIPTS=
 AM_CPPFLAGS=
 AM_CFLAGS = @TOR_SYSTEMD_CFLAGS@
 SHELL = @SHELL@
+
+if COVERAGE_ENABLED
+TESTING_TOR_BINARY="$(top_builddir)/src/or/tor-cov"
+else
+TESTING_TOR_BINARY="$(top_builddir)/src/or/tor"
+endif
+
 include src/include.am
 include doc/include.am
 include contrib/include.am
diff --git a/changes/bug17818 b/changes/bug17818
new file mode 100644
index 000000000..3d9afe329
--- /dev/null
+++ b/changes/bug17818
@@ -0,0 +1,3 @@
+  o Minor bugfixes (compilation):
+    - Isolate environment variables meant for tests from the rest of the
+      build system. Fixes bug 17818; bugfix on tor-0.2.7.3-rc.
diff --git a/src/or/include.am b/src/or/include.am
index d0e955f49..a3ac49c5d 100644
--- a/src/or/include.am
+++ b/src/or/include.am
@@ -123,9 +123,6 @@ src_or_tor_cov_LDADD = src/or/libtor-testing.a src/common/libor-testing.a \
 	src/common/libor-event-testing.a src/trunnel/libor-trunnel-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ @TOR_OPENSSL_LIBS@ \
 	@TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@ @TOR_SYSTEMD_LIBS@
-export TESTING_TOR_BINARY=$(top_builddir)/src/or/tor-cov
-else
-export TESTING_TOR_BINARY=$(top_builddir)/src/or/tor
 endif
 
 ORHEADERS = \
diff --git a/src/test/include.am b/src/test/include.am
index a37fe23db..9577e1e80 100644
--- a/src/test/include.am
+++ b/src/test/include.am
@@ -1,8 +1,9 @@
-
-export PYTHON=@PYTHON@
-export SHELL=@SHELL@
-export abs_top_srcdir=@abs_top_srcdir@
-export builddir=@builddir@
+AM_TESTS_ENVIRONMENT = \
+	export PYTHON="$(PYTHON)"; \
+	export SHELL="$(SHELL)"; \
+	export abs_top_srcdir="$(abs_top_srcdir)"; \
+	export builddir="$(builddir)"; \
+	export TESTING_TOR_BINARY="$(TESTING_TOR_BINARY)";
 
 TESTSCRIPTS = src/test/test_zero_length_keys.sh