diff --git a/dist/bin/common b/dist/bin/common
index cb0908c97563..2826e9e06708 100755
--- a/dist/bin/common
+++ b/dist/bin/common
@@ -159,8 +159,9 @@ SBT_INTF=$(find_lib "*compiler-interface*")
 JLINE_READER=$(find_lib "*jline-reader-3*")
 JLINE_TERMINAL=$(find_lib "*jline-terminal-3*")
 JLINE_TERMINAL_JNA=$(find_lib "*jline-terminal-jna-3*")
-[[ ${conemu-} ]] || JNA=$(find_lib "*jna-5*")
 
+# jna-5 only appropriate for some combinations
+[[ ${conemu-} && ${msys-} ]] || JNA=$(find_lib "*jna-5*")
 
 compilerJavaClasspathArgs () {
   # echo "dotty-compiler: $DOTTY_COMP"
diff --git a/dist/bin/scalac b/dist/bin/scalac
index fa93c41293bd..14a3998215c6 100755
--- a/dist/bin/scalac
+++ b/dist/bin/scalac
@@ -67,8 +67,10 @@ if [ "$PROG_NAME" == "$ScriptingMain" ]; then
   scripting_string="-script $target_script ${scripting_args[@]}"
 fi
 
-# exec here would prevent onExit from being called, leaving terminal in unusable state
 [ -n "$script_trace" ] && set -x
+[ -z "${ConEmuPID-}" -o -n "${cygwin-}" ] && export MSYSTEM= PWD= # workaround for #12405
+
+# exec here would prevent onExit from being called, leaving terminal in unusable state
 eval "\"$JAVACMD\"" \
    ${JAVA_OPTS:-$default_java_opts} \
    "${java_args[@]}" \