diff --git a/darshan-runtime/doc/darshan-runtime.txt b/darshan-runtime/doc/darshan-runtime.txt
index 06fdcc46621910abe196d84c98dae879403ef3a3..19a02627a473282ae0f1792aaf9171ad36224c7f 100644
--- a/darshan-runtime/doc/darshan-runtime.txt
+++ b/darshan-runtime/doc/darshan-runtime.txt
@@ -555,6 +555,7 @@ behavior at runtime:
 * DARSHAN_LOGFILE: specifies the path (directory + Darshan log file name) to write the output Darshan log to. This overrides the default Darshan behavior of automatically generating a log file name and adding it to a log file directory formatted using darshan-mk-log-dirs script.
 * DARSHAN_MODMEM: specifies the maximum amount of memory (in MiB) Darshan instrumentation modules can collectively consume at runtime (if not specified, Darshan uses a default quota of 2 MiB).
 * DARSHAN_MMAP_LOGPATH: if Darshan's mmap log file mechanism is enabled, this variable specifies what path the mmap log files should be stored in (if not specified, log files will be stored in `/tmp`).
+* DARSHAN_EXCLUDE_DIRS: specifies a list of comma-separated paths that Darshan will not instrument at runtime (in addition to Darshan's default blacklist)
 * DXT_ENABLE_IO_TRACE: setting this environment variable enables the DXT (Darshan eXtended Tracing) modules at runtime. Users can specify a numeric value for this variable to set the number of MiB to use for tracing per process; if no value is specified, Darshan will use a default value of 4 MiB.
 
 == Debugging