diff --git a/vlib/v/builder/cflags.v b/vlib/v/builder/cflags.v
index 1486f692b0..8231ed17ce 100644
--- a/vlib/v/builder/cflags.v
+++ b/vlib/v/builder/cflags.v
@@ -1,6 +1,7 @@
 module builder
 
 import os
+import v.pref
 import v.cflag
 
 // get flags for current os
@@ -14,17 +15,18 @@ fn (mut v Builder) get_os_cflags() []cflag.CFlag {
 		if flag.value.ends_with('.o') {
 			flag.cached = v.pref.cache_manager.postfix_with_key2cpath('.o', os.real_path(flag.value))
 		}
-		if flag.os == '' || (flag.os == 'linux' && v.pref.os == .linux)
-			|| (flag.os == 'macos' && v.pref.os == .macos)
-			|| (flag.os == 'darwin' && v.pref.os == .macos)
-			|| (flag.os == 'freebsd' && v.pref.os == .freebsd)
-			|| (flag.os == 'windows' && v.pref.os == .windows)
-			|| (flag.os == 'mingw' && v.pref.os == .windows && v.pref.ccompiler != 'msvc')
-			|| (flag.os == 'solaris' && v.pref.os == .solaris) {
+		if flag.os == '' || flag.os in ctimedefines {
 			flags << flag
+			continue
 		}
-		if flag.os in ctimedefines {
+		fos := pref.os_from_string(flag.os) or { pref.OS.all }
+		if fos != .all && fos == v.pref.os {
 			flags << flag
+			continue
+		}
+		if v.pref.os == .windows && flag.os == 'mingw' && v.pref.ccompiler != 'msvc' {
+			flags << flag
+			continue
 		}
 	}
 	return flags
diff --git a/vlib/v/pref/os.v b/vlib/v/pref/os.v
index 97ad947b7c..52b9dea712 100644
--- a/vlib/v/pref/os.v
+++ b/vlib/v/pref/os.v
@@ -35,6 +35,7 @@ pub fn os_from_string(os_str string) ?OS {
 		'windows' { return .windows }
 		'ios' { return .ios }
 		'macos' { return .macos }
+		'darwin' { return .macos }
 		'freebsd' { return .freebsd }
 		'openbsd' { return .openbsd }
 		'netbsd' { return .netbsd }
@@ -50,8 +51,10 @@ pub fn os_from_string(os_str string) ?OS {
 		'raw' { return .raw }
 		'nix' { return .linux }
 		'wasm32' { return .wasm32 }
-		'wasm32-wasi' { return .wasm32_wasi }
+		'wasm32-wasi' { return .wasm32_wasi } // TODO: remove these *or* the _ ones
 		'wasm32-emscripten' { return .wasm32_emscripten }
+		'wasm32_wasi' { return .wasm32_wasi }
+		'wasm32_emscripten' { return .wasm32_emscripten }
 		'' { return ._auto }
 		else { return error('bad OS $os_str') }
 	}
@@ -85,6 +88,9 @@ pub fn (o OS) str() string {
 }
 
 pub fn get_host_os() OS {
+	$if android {
+		return .android
+	}
 	$if linux {
 		return .linux
 	}