diff --git a/mongoose.c b/mongoose.c
index a22898a3..f164b5e7 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3046,8 +3046,10 @@ bool mg_file_printf(struct mg_fs *fs, const char *path, const char *fmt, ...) {
   va_start(ap, fmt);
   data = mg_vmprintf(fmt, &ap);
   va_end(ap);
-  result = mg_file_write(fs, path, data, strlen(data));
-  mg_free(data);
+  if (data != NULL) {
+    result = mg_file_write(fs, path, data, strlen(data));
+    mg_free(data);
+  }
   return result;
 }
 
diff --git a/src/fs.c b/src/fs.c
index fd9d7e6b..6df00c4a 100644
--- a/src/fs.c
+++ b/src/fs.c
@@ -67,8 +67,10 @@ bool mg_file_printf(struct mg_fs *fs, const char *path, const char *fmt, ...) {
   va_start(ap, fmt);
   data = mg_vmprintf(fmt, &ap);
   va_end(ap);
-  result = mg_file_write(fs, path, data, strlen(data));
-  mg_free(data);
+  if (data != NULL) {
+    result = mg_file_write(fs, path, data, strlen(data));
+    mg_free(data);
+  }
   return result;
 }