diff --git a/c/reg_test/expected/out b/c/reg_test/expected/out
index fc962409f..70d06b9e3 100644
--- a/c/reg_test/expected/out
+++ b/c/reg_test/expected/out
@@ -37992,6 +37992,18 @@ mlr cat then nothing ./reg_test/input/abixy ./reg_test/input/abixy
 mlr cat then nothing then cat ./reg_test/input/abixy
 
 
+================================================================
+IN-PLACE PROCESSING
+
+mlr -I --opprint head -n 2 /Users/kerl/pub_http_internet/miller-releases/miller-head/c/output-regtest/abixy.temp1 /Users/kerl/pub_http_internet/miller-releases/miller-head/c/output-regtest/abixy.temp2
+
+mlr -I --opprint head -n 2
+./reg_test/../../c/mlr: -I option (in-place operation) requires input files.
+
+mlr -I --opprint -n head -n 2 /Users/kerl/pub_http_internet/miller-releases/miller-head/c/output-regtest/abixy.temp1
+./reg_test/../../c/mlr: -I option (in-place operation) requires input files.
+
+
 ================================================================
 MAPPER TEE REDIRECTS
 
diff --git a/c/reg_test/run b/c/reg_test/run
index 7426c0af6..b983e1cd9 100755
--- a/c/reg_test/run
+++ b/c/reg_test/run
@@ -3820,6 +3820,20 @@ run_mlr tac then nothing   $indir/abixy
 run_mlr cat then nothing   $indir/abixy $indir/abixy
 run_mlr cat then nothing then cat $indir/abixy
 
+# ----------------------------------------------------------------
+announce IN-PLACE PROCESSING
+
+cp $indir/abixy $outdir/abixy.temp1
+cp $indir/abixy $outdir/abixy.temp2
+cat $outdir/abixy.temp1
+cat $outdir/abixy.temp2
+run_mlr -I --opprint head -n 2 $outdir/abixy.temp1 $outdir/abixy.temp2
+cat $outdir/abixy.temp1
+cat $outdir/abixy.temp2
+
+mlr_expect_fail -I --opprint head -n 2 < $outdir/abixy.temp1
+mlr_expect_fail -I --opprint -n head -n 2 $outdir/abixy.temp1
+
 # ----------------------------------------------------------------
 announce MAPPER TEE REDIRECTS
 
diff --git a/c/todo.txt b/c/todo.txt
index c501af943..24614d7e1 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -8,8 +8,7 @@ BUGFIXES
 
 !! non-ephemeral logic permits references to out-of-scopes ?
   -> ensure either ephemeral-transfer, or final-copy, at assignment time
-
-* mlr -I expect-fail case w/o files; -n
+  -> ephemerals must live *only* in the eval-tree
 
 * UT
 * cookbook