diff --git a/src/file_parser.rs b/src/file_parser.rs
index 77d937f..2c758bd 100644
--- a/src/file_parser.rs
+++ b/src/file_parser.rs
@@ -13,6 +13,7 @@ pub struct Filelist {
     pub incdirs: Vec<PathBuf>,
     pub defines: HashMap<String, Option<String>>,
     pub comments_present: bool,
+    pub unknowns_present: bool,
 }
 
 impl Filelist {
@@ -22,6 +23,7 @@ impl Filelist {
             incdirs: Vec::new(),
             defines: HashMap::new(),
             comments_present: false,
+            unknowns_present: false,
         }
     }
 
@@ -30,6 +32,7 @@ impl Filelist {
         self.incdirs.extend(other.incdirs);
         self.defines.extend(other.defines);
         self.comments_present |= other.comments_present;
+        self.unknowns_present |= other.unknowns_present;
     }
 }
 
@@ -58,6 +61,7 @@ pub fn parse_file(path: &str) -> Result<Filelist, Box<dyn Error>> {
                 }
             }
             LineType::Comment => filelist.comments_present = true,
+            LineType::Unknown => filelist.unknowns_present = true,
             LineType::Filelist(path) => {
                 filelist.extend(parse_file(path)?);
             }
diff --git a/src/line_parser.rs b/src/line_parser.rs
index b860577..6c4bf2d 100644
--- a/src/line_parser.rs
+++ b/src/line_parser.rs
@@ -7,7 +7,7 @@ pub enum LineType<'a> {
     Define(HashMap<&'a str, Option<&'a str>>),
     Filelist(&'a str),
     Comment,
-    // Unknown,
+    Unknown,
 }
 
 pub fn parse_line(line: &str) -> LineType {
@@ -35,6 +35,8 @@ pub fn parse_line(line: &str) -> LineType {
         LineType::IncDir(incdir_vec)
     } else if line.starts_with("//") {
         LineType::Comment
+    } else if line.starts_with('-') || line.starts_with('+') {
+        LineType::Unknown
     } else {
         // Mark everything else as a File
         LineType::File(line)
@@ -95,6 +97,18 @@ mod test {
         assert_eq!(parse_line(line), LineType::Comment);
     }
 
+    #[test]
+    fn parse_line_unknown_hyphen() {
+        let line = "-funcmd";
+        assert_eq!(parse_line(line), LineType::Unknown);
+    }
+
+    #[test]
+    fn parse_line_unknown_plus() {
+        let line = "+funcmd";
+        assert_eq!(parse_line(line), LineType::Unknown);
+    }
+
     #[test]
     fn parse_line_file() {
         let line = "any_random_line_is_a_file";
diff --git a/tests/integration_tests.rs b/tests/integration_tests.rs
index 7059339..678fbef 100644
--- a/tests/integration_tests.rs
+++ b/tests/integration_tests.rs
@@ -22,6 +22,7 @@ fn simple_test() {
         incdirs: vec![PathBuf::from("testcase/")],
         defines: defines,
         comments_present: true,
+        unknowns_present: false,
     };
 
     // Add env vars