diff --git a/usage.c b/usage.c
index 17f52c1b5c..ad6d2910fb 100644
--- a/usage.c
+++ b/usage.c
@@ -7,21 +7,19 @@
 #include "cache.h"
 
 static FILE *error_handle;
-static int tweaked_error_buffering;
 
 void vreportf(const char *prefix, const char *err, va_list params)
 {
+	char msg[4096];
 	FILE *fh = error_handle ? error_handle : stderr;
+	char *p;
 
-	fflush(fh);
-	if (!tweaked_error_buffering) {
-		setvbuf(fh, NULL, _IOLBF, 0);
-		tweaked_error_buffering = 1;
+	vsnprintf(msg, sizeof(msg), err, params);
+	for (p = msg; *p; p++) {
+		if (iscntrl(*p) && *p != '\t' && *p != '\n')
+			*p = '?';
 	}
-
-	fputs(prefix, fh);
-	vfprintf(fh, err, params);
-	fputc('\n', fh);
+	fprintf(fh, "%s%s\n", prefix, msg);
 }
 
 static NORETURN void usage_builtin(const char *err, va_list params)
@@ -93,7 +91,6 @@ void set_die_is_recursing_routine(int (*routine)(void))
 void set_error_handle(FILE *fh)
 {
 	error_handle = fh;
-	tweaked_error_buffering = 0;
 }
 
 void NORETURN usagef(const char *err, ...)