diff --git a/tox.ini b/tox.ini
index 0baf40ef5cf..d3d96b2039b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -38,6 +38,10 @@ conda_deps=
     gsl
     lapack==3.6.1
 conda_channels=conda-forge
+setenv =
+    ; Tell the linker to look for shared libs inside the temporary Conda env.
+    ; Needed to build BBHx's wheel, whick links to LAPACK.
+    LIBRARY_PATH={envdir}/lib:{env:LIBRARY_PATH:}
 commands = pytest
 
 # The following are long running or may require
@@ -81,5 +85,9 @@ conda_deps=
     lapack==3.6.1
     openmpi
 conda_channels=conda-forge
-setenv = PYCBC_TEST_TYPE=docs
+setenv =
+    PYCBC_TEST_TYPE=docs
+    ; Tell the linker to look for shared libs inside the temporary Conda env.
+    ; Needed to build BBHx's wheel, whick links to LAPACK.
+    LIBRARY_PATH={envdir}/lib:{env:LIBRARY_PATH:}
 commands = bash tools/pycbc_test_suite.sh