diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 5d41e1bb1b2..230b1023422 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -350,6 +350,9 @@ class TypesTests(unittest.TestCase):
         test(1234567, ',', '1,234,567')
         test(-1234567, ',', '-1,234,567')
 
+        # issue 5782, commas with no specifier type
+        test(1234, '010,', '00,001,234')
+
         # make sure these are errors
 
         # precision disallowed
@@ -567,6 +570,9 @@ class TypesTests(unittest.TestCase):
         test(-1234.12341234, '013f', '-01234.123412')
         test(-123456.12341234, '011.2f', '-0123456.12')
 
+        # issue 5782, commas with no specifier type
+        test(1.2, '010,.2', '0,000,001.2')
+
         # 0 padding with commas
         test(1234., '011,f', '1,234.000000')
         test(1234., '012,f', '1,234.000000')
diff --git a/Objects/stringlib/formatter.h b/Objects/stringlib/formatter.h
index 61ca12badf8..9cbd2cc9310 100644
--- a/Objects/stringlib/formatter.h
+++ b/Objects/stringlib/formatter.h
@@ -248,6 +248,7 @@ parse_internal_render_format_spec(STRINGLIB_CHAR *format_spec,
         case 'G':
         case '%':
         case 'F':
+        case '\0':
             /* These are allowed. See PEP 378.*/
             break;
         default: