diff --git a/t/t0050-filesystem.sh b/t/t0050-filesystem.sh
index 057c97c49f..1542cf6a13 100755
--- a/t/t0050-filesystem.sh
+++ b/t/t0050-filesystem.sh
@@ -4,8 +4,8 @@ test_description='Various filesystem issues'
 
 . ./test-lib.sh
 
-auml=`printf '\xc3\xa4'`
-aumlcdiar=`printf '\x61\xcc\x88'`
+auml=$(printf '\303\244')
+aumlcdiar=$(printf '\141\314\210')
 
 case_insensitive=
 unibad=
diff --git a/t/t3419-rebase-patch-id.sh b/t/t3419-rebase-patch-id.sh
index 1aee483510..bd8efaf005 100755
--- a/t/t3419-rebase-patch-id.sh
+++ b/t/t3419-rebase-patch-id.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 test_description='git rebase - test patch id computation'
 
@@ -27,7 +27,7 @@ scramble()
 		then
 			echo "$x"
 		fi
-		i=$(((i+1) % 10))
+		i=$((($i+1) % 10))
 	done < "$1" > "$1.new"
 	mv -f "$1.new" "$1"
 }
diff --git a/trace.c b/trace.c
index 62586fa371..0fb2a2c64b 100644
--- a/trace.c
+++ b/trace.c
@@ -25,10 +25,6 @@
 #include "cache.h"
 #include "quote.h"
 
-static void do_nothing(size_t unused)
-{
-}
-
 /* Get a trace file descriptor from GIT_TRACE env variable. */
 static int get_trace_fd(int *need_close)
 {
@@ -76,7 +72,7 @@ void trace_printf(const char *fmt, ...)
 	if (!fd)
 		return;
 
-	set_try_to_free_routine(do_nothing);	/* is never reset */
+	set_try_to_free_routine(NULL);	/* is never reset */
 	strbuf_init(&buf, 64);
 	va_start(ap, fmt);
 	len = vsnprintf(buf.buf, strbuf_avail(&buf), fmt, ap);
@@ -108,7 +104,7 @@ void trace_argv_printf(const char **argv, const char *fmt, ...)
 	if (!fd)
 		return;
 
-	set_try_to_free_routine(do_nothing);	/* is never reset */
+	set_try_to_free_routine(NULL);	/* is never reset */
 	strbuf_init(&buf, 64);
 	va_start(ap, fmt);
 	len = vsnprintf(buf.buf, strbuf_avail(&buf), fmt, ap);
diff --git a/wrapper.c b/wrapper.c
index 4c1639f153..8d7dd31c4b 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -12,6 +12,8 @@ static void (*try_to_free_routine)(size_t size) = do_nothing;
 try_to_free_t set_try_to_free_routine(try_to_free_t routine)
 {
 	try_to_free_t old = try_to_free_routine;
+	if (!routine)
+		routine = do_nothing;
 	try_to_free_routine = routine;
 	return old;
 }