diff --git a/src/base/cprintf_formats.hh b/src/base/cprintf_formats.hh
index 5b3b344325..253fe59cfc 100644
--- a/src/base/cprintf_formats.hh
+++ b/src/base/cprintf_formats.hh
@@ -151,6 +151,9 @@ _format_float(std::ostream &out, const T &data, Format &fmt)
 
     ios::fmtflags flags(out.flags());
 
+    if (fmt.fill_zero)
+        out.fill('0');
+
     switch (fmt.float_format) {
       case Format::scientific:
         if (fmt.precision != -1) {