diff --git a/src/grib_accessor_class_ascii.cc b/src/grib_accessor_class_ascii.cc
index 9d88fa9f9..b0c90182e 100644
--- a/src/grib_accessor_class_ascii.cc
+++ b/src/grib_accessor_class_ascii.cc
@@ -147,19 +147,19 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
     grib_handle* hand = grib_handle_of_accessor(a);
     const size_t alen = a->length;
 
-    if (len[0] < (alen + 1)) {
+    if (*len < (alen + 1)) {
         const char* cclass_name = a->cclass->name;
         grib_context_log(a->context, GRIB_LOG_ERROR,
                          "%s: Buffer too small for %s. It is %zu bytes long (len=%zu)",
                          cclass_name, a->name, alen+1, *len);
-        len[0] = alen + 1;
+        *len = alen + 1;
         return GRIB_BUFFER_TOO_SMALL;
     }
 
     for (i = 0; i < alen; i++)
         val[i] = hand->buffer->data[a->offset + i];
     val[i] = 0;
-    len[0] = i;
+    *len = i;
     return GRIB_SUCCESS;
 }
 
diff --git a/src/grib_accessor_class_bitmap.cc b/src/grib_accessor_class_bitmap.cc
index b3c371a35..bd52d16cd 100644
--- a/src/grib_accessor_class_bitmap.cc
+++ b/src/grib_accessor_class_bitmap.cc
@@ -297,7 +297,7 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
         val[i] = hand->buffer->data[a->offset + i];
     }
 
-    len[0] = a->length;
+    *len = a->length;
 
     return GRIB_SUCCESS;
 }
diff --git a/src/grib_accessor_class_non_alpha.cc b/src/grib_accessor_class_non_alpha.cc
index 55ee9f917..f324257fe 100644
--- a/src/grib_accessor_class_non_alpha.cc
+++ b/src/grib_accessor_class_non_alpha.cc
@@ -149,20 +149,20 @@ static int get_native_type(grib_accessor* a)
 static int unpack_string(grib_accessor* a, char* val, size_t* len)
 {
     grib_handle* hand = grib_handle_of_accessor(a);
-    int i             = 0;
+    long i = 0;
 
-    if (len[0] < (a->length + 1)) {
-        grib_context_log(a->context, GRIB_LOG_ERROR, "unpack_string: Wrong size (%lu) for %s it contains %ld values",
-                len[0], a->name, a->length + 1);
-        len[0] = 0;
-        return GRIB_ARRAY_TOO_SMALL;
+    if (*len < (a->length + 1)) {
+        grib_context_log(a->context, GRIB_LOG_ERROR, "unpack_string: Wrong size (%lu) for %s, it contains %ld values",
+                *len, a->name, a->length + 1);
+        *len = a->length + 1;
+        return GRIB_BUFFER_TOO_SMALL;
     }
 
     for (i = 0; i < a->length; i++) {
         val[i] = hand->buffer->data[a->offset + i];
     }
     val[i] = 0;
-    len[0] = i;
+    *len = i;
     return GRIB_SUCCESS;
 }
 
diff --git a/src/grib_accessor_class_to_double.cc b/src/grib_accessor_class_to_double.cc
index c9725e52d..69b06add9 100644
--- a/src/grib_accessor_class_to_double.cc
+++ b/src/grib_accessor_class_to_double.cc
@@ -166,18 +166,17 @@ static int get_native_type(grib_accessor* a)
 
 static int unpack_string(grib_accessor* a, char* val, size_t* len)
 {
-    int err                       = 0;
     grib_accessor_to_double* self = (grib_accessor_to_double*)a;
-    char buff[512]                = {0,};
-    size_t length;
+
+    int err = 0;
+    char buff[512] = {0,};
     size_t size = 512;
+    size_t length = string_length(a);
 
-    length = string_length(a);
-
-    if (len[0] < length + 1) {
+    if (*len < length + 1) {
         grib_context_log(a->context, GRIB_LOG_ERROR, "unpack_string: Wrong size (%lu) for %s, it contains %ld values",
-                len[0], a->name, a->length + 1);
-        len[0] = 0;
+                *len, a->name, a->length + 1);
+        *len = length + 1;
         return GRIB_ARRAY_TOO_SMALL;
     }
 
@@ -192,7 +191,7 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
     memcpy(val, buff + self->start, length);
 
     val[length] = 0;
-    len[0]      = length;
+    *len = length;
     return err;
 }
 
diff --git a/src/grib_accessor_class_to_integer.cc b/src/grib_accessor_class_to_integer.cc
index 787b122b8..76ce1205d 100644
--- a/src/grib_accessor_class_to_integer.cc
+++ b/src/grib_accessor_class_to_integer.cc
@@ -164,19 +164,21 @@ static int get_native_type(grib_accessor* a)
 
 static int unpack_string(grib_accessor* a, char* val, size_t* len)
 {
-    int err                        = 0;
     grib_accessor_to_integer* self = (grib_accessor_to_integer*)a;
-    char buff[512]                 = {0,};
-    size_t length;
+
+    int err = 0;
+    char buff[512] = {0,};
     size_t size = 512;
 
-    length = string_length(a);
+    size_t length = string_length(a);
 
-    if (len[0] < length + 1) {
-        grib_context_log(a->context, GRIB_LOG_ERROR, "unpack_string: Wrong size (%lu) for %s, it contains %ld values",
-                len[0], a->name, a->length + 1);
-        len[0] = 0;
-        return GRIB_ARRAY_TOO_SMALL;
+    if (*len < length + 1) {
+        const char* cclass_name = a->cclass->name;
+        grib_context_log(a->context, GRIB_LOG_ERROR,
+                         "%s: Buffer too small for %s. It is %zu bytes long (len=%zu)",
+                         cclass_name, a->name, length+1, *len);
+        *len = length + 1;
+        return GRIB_BUFFER_TOO_SMALL;
     }
 
     err = grib_get_string(grib_handle_of_accessor(a), self->key, buff, &size);
@@ -190,7 +192,7 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
     memcpy(val, buff + self->start, length);
 
     val[length] = 0;
-    len[0]      = length;
+    *len = length;
     return GRIB_SUCCESS;
 }
 
diff --git a/src/grib_accessor_class_to_string.cc b/src/grib_accessor_class_to_string.cc
index 818ad386d..648edd1aa 100644
--- a/src/grib_accessor_class_to_string.cc
+++ b/src/grib_accessor_class_to_string.cc
@@ -163,16 +163,18 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
 {
     grib_accessor_to_string* self = (grib_accessor_to_string*)a;
 
-    int err        = 0;
+    int err = 0;
     char buff[512] = {0,};
 
     size_t length = string_length(a);
 
-    if (len[0] < length + 1) {
-        grib_context_log(a->context, GRIB_LOG_ERROR, "unpack_string: Wrong size (%lu) for %s, it contains %ld values",
-                         len[0], a->name, a->length + 1);
-        len[0] = 0;
-        return GRIB_ARRAY_TOO_SMALL;
+    if (*len < length + 1) {
+        const char* cclass_name = a->cclass->name;
+        grib_context_log(a->context, GRIB_LOG_ERROR,
+                         "%s: Buffer too small for %s. It is %zu bytes long (len=%zu)",
+                         cclass_name, a->name, length+1, *len);
+        *len = length + 1;
+        return GRIB_BUFFER_TOO_SMALL;
     }
 
     size_t size = sizeof(buff);
@@ -187,7 +189,7 @@ static int unpack_string(grib_accessor* a, char* val, size_t* len)
     memcpy(val, buff + self->start, length);
 
     val[length] = 0;
-    len[0]      = length;
+    *len = length;
     return GRIB_SUCCESS;
 }
 
diff --git a/tests/codes_get_string.cc b/tests/codes_get_string.cc
index 2cc90798a..d0cf15192 100644
--- a/tests/codes_get_string.cc
+++ b/tests/codes_get_string.cc
@@ -35,8 +35,10 @@ int main(int argc, char* argv[])
     len = 1; // Cause it to fail
 
     err = codes_get_string(h, key, kvalue, &len);
-    printf("err=%d  kvalue=|%s|\n", err, kvalue);
+    //printf("err=%d  kvalue=|%s|\n", err, kvalue);
     assert(err == CODES_BUFFER_TOO_SMALL);
+    // The correct len should have been set
+    assert(len > 1);
 
     codes_handle_delete(h);
     fclose(in);