diff --git a/src/bindings/py_str.c b/src/bindings/py_str.c
index 7b71de89..ea300b72 100644
--- a/src/bindings/py_str.c
+++ b/src/bindings/py_str.c
@@ -447,6 +447,12 @@ static bool str_zfill(int argc, py_Ref argv) {
     }
     c11_sbuf buf;
     c11_sbuf__ctor(&buf);
+    // a leading sign is kept in front; the padding goes after it
+    if(self.size > 0 && (self.data[0] == '+' || self.data[0] == '-')) {
+        c11_sbuf__write_char(&buf, self.data[0]);
+        self.data++;
+        self.size--;
+    }
     for(int i = 0; i < delta; i++) {
         c11_sbuf__write_char(&buf, '0');
     }
diff --git a/tests/041_str.py b/tests/041_str.py
index 475d15c2..f7fda43a 100644
--- a/tests/041_str.py
+++ b/tests/041_str.py
@@ -112,6 +112,9 @@ assert s2.join( seq ) == "runoob"
 
 assert 'x'.zfill(5) == '0000x'
 assert '568'.zfill(1) == '568'
+assert '-5'.zfill(4) == '-005'
+assert '+5'.zfill(4) == '+005'
+assert '-'.zfill(3) == '-00'
 
 num = 6
 assert str(num) == '6'