1 files changed, 1 insertions, 0 deletions
diff --git a/lib/sendf.c b/lib/sendf.c
index 04cc725f5..adcee89f8 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -267,6 +267,7 @@ void Curl_infof(struct Curl_easy *data, const char *fmt, ...)
 
 void Curl_failf(struct Curl_easy *data, const char *fmt, ...)
 {
+  DEBUGASSERT(!strchr(fmt, '\n'));
   if(data->set.verbose || data->set.errorbuffer) {
     va_list ap;
     size_t len;