diff --git a/vlib/compiler/cflags.v b/vlib/compiler/cflags.v
index 5e658b1042..d20fe4abe4 100644
--- a/vlib/compiler/cflags.v
+++ b/vlib/compiler/cflags.v
@@ -70,15 +70,16 @@ fn (table &Table) has_cflag(cflag CFlag) bool {
 
 // parse the flags to (table.cflags) []CFlag
 // Note: clean up big time (joe-c)
-fn (table mut Table) parse_cflag(cflag string, mod string) {
+fn (table mut Table) parse_cflag(cflag string, mod string) ?bool {
 	allowed_flags := [
 		'framework',
 		'library',
 		'I', 'l', 'L',
 	]
-	mut flag := cflag.trim_space()
+	flag_orig := cflag.trim_space()
+	mut flag := flag_orig
 	if flag == '' {
-		return
+		return true
 	}
 	mut fos := ''
 	mut name := ''
@@ -124,6 +125,13 @@ fn (table mut Table) parse_cflag(cflag string, mod string) {
 			value = flag.trim_space()
 			index = -1
 		}
+		if (name in ['-I', '-l', '-L']) && value == '' {
+			if name == '-I' || name == '-L' {
+				return error('bad #flag `$flag_orig`: missing path after `-I`')
+			} else if name == '-l' {
+				return error('bad #flag `$flag_orig`: missing library name after `-l`')
+			}
+		} 
 		cf := CFlag{
 			mod:   mod,
 			os:    fos,
@@ -137,7 +145,7 @@ fn (table mut Table) parse_cflag(cflag string, mod string) {
 			break
 		}
 	}
-	return
+	return true
 }
 
 //TODO: implement msvc specific c_options_before_target and c_options_after_target ...