diff --git a/backend/code1.c b/backend/code1.c
index 4af521b4..245f53d6 100644
--- a/backend/code1.c
+++ b/backend/code1.c
@@ -316,7 +316,7 @@ static int c1_look_ahead_test(const unsigned char source[], const int sourcelen,
 
 /* Whether can fit last character or characters in a single ASCII codeword */
 static int is_last_single_ascii(const unsigned char string[], const int length, const int sp) {
-    if (length - sp == 1 && string[sp + 1] <= 127) {
+    if (length - sp == 1 && string[sp] <= 127) {
         return 1;
     }
     if (length - sp == 2 && istwodigits(string, length, sp)) {
diff --git a/backend/tests/test_code1.c b/backend/tests/test_code1.c
index 629e1f0c..f433b86b 100644
--- a/backend/tests/test_code1.c
+++ b/backend/tests/test_code1.c
@@ -2568,7 +2568,6 @@ static void test_encode(int index, int generate, int debug) {
     testFinish();
 }
 
-// #181 Nico Gunkel OSS-Fuzz
 static void test_fuzz(int index, int debug) {
 
     struct item {
@@ -2578,7 +2577,8 @@ static void test_fuzz(int index, int debug) {
     };
     // s/\/\*[ 0-9]*\*\//\=printf("\/*%2d*\/", line(".") - line("'<"))
     struct item data[] = {
-        /* 0*/ { "3333P33B\035333V3333333333333\0363", -1, 0 },
+        /* 0*/ { "3333P33B\035333V3333333333333\0363", -1, 0 }, // #181 Nico Gunkel, OSS-Fuzz
+        /* 1*/ { "{{-06\024755712162106130000000829203983\377", -1, 0 }, // #232 Jan Schrewe, CI-Fuzz, out-of-bounds in is_last_single_ascii() sp + 1
     };
     int data_size = ARRAY_SIZE(data);
     int i, length, ret;