diff --git a/ext/standard/math.c b/ext/standard/math.c
index b3e8c6f086c0e..6e934a3857a7c 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -1120,6 +1120,10 @@ static char *_php_math_number_format_ex_len(double d, int dec, char *dec_point,
 	tmplen = spprintf(&tmpbuf, 0, "%.*F", dec, d);
 
 	if (tmpbuf == NULL || !isdigit((int)tmpbuf[0])) {
+		if (result_len) {
+			*result_len = tmplen;
+		}
+
 		return tmpbuf;
 	}
 
diff --git a/ext/standard/tests/general_functions/bug27678.phpt b/ext/standard/tests/general_functions/bug27678.phpt
index 5db5890a1ce5b..6f95509e14efe 100644
--- a/ext/standard/tests/general_functions/bug27678.phpt
+++ b/ext/standard/tests/general_functions/bug27678.phpt
@@ -6,9 +6,11 @@ Bug #27678 (number_format() crashes with large numbers)
 number_format(1e80, 0, '', ' ');
 number_format(1e300, 0, '', ' ');
 number_format(1e320, 0, '', ' ');
-number_format(1e1000, 0, '', ' ');
+$num = number_format(1e1000, 0, '', ' ');
+var_dump(strlen($num) == 3); // $num == 'inf'
 
 echo "Done\n";
 ?>
 --EXPECT--	
+bool(true)
 Done