diff --git a/cmd/tools/check_os_api_parity.v b/cmd/tools/check_os_api_parity.v
index 9eb73a08f9..4980dde63e 100644
--- a/cmd/tools/check_os_api_parity.v
+++ b/cmd/tools/check_os_api_parity.v
@@ -5,6 +5,7 @@ import v.util
 import v.pref
 import v.builder
 import v.ast
+import rand
 import term
 
 const (
@@ -116,7 +117,7 @@ fn (app App) gen_api_for_module_in_os(mod_name string, os_name string) string {
 }
 
 fn (mut app App) compare_api(api_base string, api_os string, mod_name string, os_base string, os_target string) {
-	res := util.color_compare_strings(app.diff_cmd, api_base, api_os)
+	res := util.color_compare_strings(app.diff_cmd, rand.ulid(), api_base, api_os)
 	if res.len > 0 {
 		summary := 'Different APIs found for module: `$mod_name`, between OS base: `$os_base` and OS: `$os_target`'
 		eprintln(term.header(summary, '-'))
diff --git a/cmd/tools/vvet/vet_test.v b/cmd/tools/vvet/vet_test.v
index b4e292fa33..9bb6443950 100644
--- a/cmd/tools/vvet/vet_test.v
+++ b/cmd/tools/vvet/vet_test.v
@@ -1,4 +1,5 @@
 import os
+import rand
 import term
 import v.util.vtest
 import v.util
@@ -51,7 +52,7 @@ fn check_path(vexe string, dir string, tests []string) int {
 			println(found)
 			println('============\n')
 			println('diff:')
-			println(util.color_compare_strings(diff_cmd, found, expected))
+			println(util.color_compare_strings(diff_cmd, rand.ulid(), found, expected))
 			println('============\n')
 			nb_fail++
 		} else {
diff --git a/vlib/os/os_c.v b/vlib/os/os_c.v
index 5c4e2cc77c..7fe3503d0d 100644
--- a/vlib/os/os_c.v
+++ b/vlib/os/os_c.v
@@ -536,7 +536,7 @@ pub fn on_segfault(f voidptr) {
 		return
 	}
 	$if macos {
-		C.printf('TODO')
+		C.printf(c'TODO')
 		/*
 		mut sa := C.sigaction{}
 		C.memset(&sa, 0, sizeof(C.sigaction_size))
diff --git a/vlib/v/compiler_errors_test.v b/vlib/v/compiler_errors_test.v
index 7e9bd3665a..16f42d83b9 100644
--- a/vlib/v/compiler_errors_test.v
+++ b/vlib/v/compiler_errors_test.v
@@ -1,4 +1,5 @@
 import os
+import rand
 import term
 import v.util
 import v.util.vtest
@@ -315,7 +316,7 @@ fn clean_line_endings(s string) string {
 fn diff_content(s1 string, s2 string) {
 	diff_cmd := util.find_working_diff_command() or { return }
 	println(term.bold(term.yellow('diff: ')))
-	println(util.color_compare_strings(diff_cmd, s1, s2))
+	println(util.color_compare_strings(diff_cmd, rand.ulid(), s1, s2))
 	println('============\n')
 }
 
diff --git a/vlib/v/tests/inout/compiler_test.v b/vlib/v/tests/inout/compiler_test.v
index 7545db39ea..1cd0f5f4a1 100644
--- a/vlib/v/tests/inout/compiler_test.v
+++ b/vlib/v/tests/inout/compiler_test.v
@@ -2,6 +2,7 @@
 // To test a panic, remove everything after the long `===` line
 // You can also remove the line with 'line:' e.g. for a builtin fn
 import os
+import rand
 import term
 import v.util
 import v.util.vtest
@@ -77,7 +78,7 @@ fn test_all() {
 			println(found)
 			if diff_cmd != '' {
 				println(term.header('difference:', '-'))
-				println(util.color_compare_strings(diff_cmd, expected, found))
+				println(util.color_compare_strings(diff_cmd, rand.ulid(), expected, found))
 			} else {
 				println(term.h_divider('-'))
 			}
diff --git a/vlib/v/util/diff.v b/vlib/v/util/diff.v
index 167f3c2c1f..b3e2c6f509 100644
--- a/vlib/v/util/diff.v
+++ b/vlib/v/util/diff.v
@@ -68,11 +68,11 @@ pub fn color_compare_files(diff_cmd string, file1 string, file2 string) string {
 	return ''
 }
 
-pub fn color_compare_strings(diff_cmd string, expected string, found string) string {
+pub fn color_compare_strings(diff_cmd string, unique_prefix string, expected string, found string) string {
 	cdir := os.cache_dir()
 	ctime := time.sys_mono_now()
-	e_file := os.join_path(cdir, '${ctime}.expected.txt')
-	f_file := os.join_path(cdir, '${ctime}.found.txt')
+	e_file := os.join_path(cdir, '${unique_prefix}_${ctime}.expected.txt')
+	f_file := os.join_path(cdir, '${unique_prefix}_${ctime}.found.txt')
 	os.write_file(e_file, expected) or { panic(err) }
 	os.write_file(f_file, found) or { panic(err) }
 	res := color_compare_files(diff_cmd, e_file, f_file)