diff --git a/cmd/tools/modules/testing/common.v b/cmd/tools/modules/testing/common.v
index 34fe57f9bb..9a43588934 100644
--- a/cmd/tools/modules/testing/common.v
+++ b/cmd/tools/modules/testing/common.v
@@ -885,8 +885,7 @@ pub const is_started_mysqld = find_started_process('mysqld') or { '' }
 pub const is_started_postgres = find_started_process('postgres') or { '' }
 
 pub fn (mut ts TestSession) setup_build_environment() {
-	facts := os.getenv('VBUILD_FACTS').split_any(',')
-	mut defines := os.getenv('VBUILD_DEFINES').split_any(',')
+	facts, mut defines := pref.get_build_facts_and_defines()
 	// add the runtime information, that the test runner has already determined by checking once:
 	if is_started_mysqld != '' {
 		defines << 'started_mysqld'
diff --git a/cmd/v/v.v b/cmd/v/v.v
index e97ab61eef..2df96d6498 100644
--- a/cmd/v/v.v
+++ b/cmd/v/v.v
@@ -241,18 +241,7 @@ fn setup_vbuild_env_vars(prefs &pref.Preferences) {
 	if github_job != '' {
 		facts << github_job
 	}
-	sfacts := facts.join(',')
-	os.setenv('VBUILD_FACTS', sfacts, true)
-
-	sdefines := prefs.compile_defines_all.join(',')
-	os.setenv('VBUILD_DEFINES', sdefines, true)
-
-	$if trace_vbuild ? {
-		eprintln('> VBUILD_FACTS: ${sfacts}')
-		eprintln('> VBUILD_DEFINES: ${sdefines}')
-	}
-	unsafe { sdefines.free() }
-	unsafe { sfacts.free() }
+	pref.set_build_flags_and_defines(facts, prefs.compile_defines_all)
 	unsafe { github_job.free() }
 	unsafe { facts.free() }
 }
diff --git a/vlib/v/pref/build_flags.v b/vlib/v/pref/build_flags.v
new file mode 100644
index 0000000000..16ef907fa7
--- /dev/null
+++ b/vlib/v/pref/build_flags.v
@@ -0,0 +1,23 @@
+module pref
+
+import os
+
+pub fn get_build_facts_and_defines() ([]string, []string) {
+	facts := os.getenv('VBUILD_FACTS').split_any(',')
+	defines := os.getenv('VBUILD_DEFINES').split_any(',')
+	return facts, defines
+}
+
+@[manualfree]
+pub fn set_build_flags_and_defines(facts []string, defines []string) {
+	sfacts := facts.join(',')
+	sdefines := defines.join(',')
+	os.setenv('VBUILD_FACTS', sfacts, true)
+	os.setenv('VBUILD_DEFINES', sdefines, true)
+	$if trace_vbuild ? {
+		eprintln('> VBUILD_FACTS: ${sfacts}')
+		eprintln('> VBUILD_DEFINES: ${sdefines}')
+	}
+	unsafe { sdefines.free() }
+	unsafe { sfacts.free() }
+}