diff --git a/cmd/v/v.v b/cmd/v/v.v
index 3c76ede26b..1c2561090e 100644
--- a/cmd/v/v.v
+++ b/cmd/v/v.v
@@ -148,28 +148,4 @@ fn create_symlink() {
 	}
 }
 
-fn parse_define(prefs mut pref.Preferences, define string) {
-    define_parts := define.split('=')
-    if define_parts.len == 1 {
-        prefs.compile_defines << define
-        prefs.compile_defines_all << define
-        return
-    }
-    if define_parts.len == 2 {
-        prefs.compile_defines_all << define_parts[0]
-        match define_parts[1] {
-            '0' {}
-            '1' {
-                prefs.compile_defines << define_parts[0]
-            }
-            else {
-                println('V error: Unknown define argument value `${define_parts[1]}` for ${define_parts[0]}.' +
-                    'Expected `0` or `1`.')
-                exit(1)
-            }
-        }
-        return
-    }
-    println('V error: Unknown define argument: ${define}. Expected at most one `=`.')
-    exit(1)
-}
+
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 005f033db4..1bece8c39c 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -285,3 +285,29 @@ pub fn backend_from_string(s string) ?Backend {
 		}
 	}
 }
+
+fn parse_define(prefs mut Preferences, define string) {
+    define_parts := define.split('=')
+    if define_parts.len == 1 {
+        prefs.compile_defines << define
+        prefs.compile_defines_all << define
+        return
+    }
+    if define_parts.len == 2 {
+        prefs.compile_defines_all << define_parts[0]
+        match define_parts[1] {
+            '0' {}
+            '1' {
+                prefs.compile_defines << define_parts[0]
+            }
+            else {
+                println('V error: Unknown define argument value `${define_parts[1]}` for ${define_parts[0]}.' +
+                    'Expected `0` or `1`.')
+                exit(1)
+            }
+        }
+        return
+    }
+    println('V error: Unknown define argument: ${define}. Expected at most one `=`.')
+    exit(1)
+}