diff --git a/src/include/OpenImageIO/detail/fmt.h b/src/include/OpenImageIO/detail/fmt.h
index de4edb0744..0f264a92ba 100644
--- a/src/include/OpenImageIO/detail/fmt.h
+++ b/src/include/OpenImageIO/detail/fmt.h
@@ -148,7 +148,7 @@ struct index_formatter : format_parser_with_separator {
 // fmtlib custom formatter that formats a type `T` as if it were an array
 // `Elem[Size]` (and it must be laid out that way in memory). The formatting
 // spec will apply to each element. For example, if the object has 3 float
-// elements and the spec is "{.3f}", then the output might be "1.234 2.345
+// elements and the spec is "{:.3f}", then the output might be "1.234 2.345
 // 3.456".
 //
 // In addition to the usual formatting spec, we also recognize the following
diff --git a/src/oiiotool/printinfo.cpp b/src/oiiotool/printinfo.cpp
index 7d956fd9b4..1be4d32ecb 100644
--- a/src/oiiotool/printinfo.cpp
+++ b/src/oiiotool/printinfo.cpp
@@ -356,7 +356,7 @@ print_info_subimage(std::ostream& out, Oiiotool& ot, int current_subimage,
             if (opt.sum) {
                 imagesize_t imagebytes = spec.image_bytes(true);
                 // totalsize += imagebytes;
-                lines[0] += format(" ({.2f} MB)",
+                lines[0] += format(" ({:.2f} MB)",
                                    (float)imagebytes / (1024.0 * 1024.0));
             }
             std::string file_format_name;