diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index dc80135..1c50809 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -61,7 +61,9 @@
             continue;
         }
 
-        if( str[i] < '0' || str[i] > '9' )
+        if( ! ( ( str[i] >= '0' && str[i] <= '9' ) ||
+                ( hex && ( ( str[i] >= 'a' && str[i] <= 'f' ) ||
+                           ( str[i] >= 'A' && str[i] <= 'F' ) ) ) ) )
         {
             digits = 0;
             break;
diff --git a/tests/suites/test_suite_error.data b/tests/suites/test_suite_error.data
index 1a9997e..2caa358 100644
--- a/tests/suites/test_suite_error.data
+++ b/tests/suites/test_suite_error.data
@@ -14,8 +14,8 @@
 error_strerror:-0x8880:"UNKNOWN ERROR CODE (8880)"
 
 Non existing low error
-error_strerror:-0x0001:"UNKNOWN ERROR CODE (0001)"
+error_strerror:-0x007F:"UNKNOWN ERROR CODE (007F)"
 
 Non existing low and high error
-error_strerror:-0x8881:"UNKNOWN ERROR CODE (8880) \: UNKNOWN ERROR CODE (0001)"
+error_strerror:-0x88FF:"UNKNOWN ERROR CODE (8880) \: UNKNOWN ERROR CODE (007F)"