diff --git a/tests/run.in b/tests/run.in
index e86943b6d..dd053011d 100755
--- a/tests/run.in
+++ b/tests/run.in
@@ -46,7 +46,8 @@ PATH="@abs_top_builddir@/bin:$PATH"
 export PATH
 
 test -z "$1" &&
-    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath exec $PREFIXCMD @PYTHON@
+    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath:$DYLD_LIBRARY_PATH \
+    exec $PREFIXCMD @PYTHON@
 srcdir="@srcdir@"
 
 # Reset CFLAGS, because some tests call the compiler, and we do not
@@ -103,18 +104,18 @@ export srcdir
 
 case $1 in
   *.ipynb)
-    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath \
+    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath:$DYLD_LIBRARY_PATH \
     PYTHONIOENCODING=utf-8:surrogateescape \
     exec $PREFIXCMD @PYTHON@ @abs_srcdir@/python/ipnbdoctest.py "$@";;
   *.py)
-    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath \
+    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath:$DYLD_LIBRARY_PATH \
     exec $PREFIXCMD @PYTHON@ "$@";;
   *.test)
     exec sh -x "$@";;
   *.pl)
     exec $PERL "$@";;
   *python*|*jupyter*)
-    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath \
+    PYTHONPATH=$pypath DYLD_LIBRARY_PATH=$modpath:$DYLD_LIBRARY_PATH \
     exec $PREFIXCMD "$@";;
   *)
     echo "Unknown extension" >&2