diff --git a/misc/testsuite/mimic_ctest.sh b/misc/testsuite/mimic_ctest.sh
index d8e8d2b0..2881ff4b 100755
--- a/misc/testsuite/mimic_ctest.sh
+++ b/misc/testsuite/mimic_ctest.sh
@@ -16,6 +16,12 @@ argv0=$0; argv0abs=$(readlink -fn "$argv0"); argv0dir=$(dirname "$argv0abs")
 #   $upx_exe_runner         (e.g. "qemu-x86_64 -cpu Nehalem" or "valgrind")
 #
 
+# Debugging aid for locating failing commands.  Depends on 'bash' shell.
+# (BASH_LINENO is relative to current FUNCTION only; non-function ==> 0)
+# Notice single-quoting of entire first argument.
+trap 'echo ERROR: pwd=\"$PWD\"  file=\"$BASH_SOURCE\"  line=${BASH_LINENO[0]}  cmd=\"$BASH_COMMAND\"' ERR
+# Example: "false a b c" ==> ERROR: pwd="path/misc/testsuite" file="./mimic_ctest.sh" line=0 cmd="false a b c"
+
 #***********************************************************************
 # init & checks
 #***********************************************************************