diff --git a/src/lib.rs b/src/lib.rs
index d4ce110..daf7023 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -140,6 +140,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .map_or(Default::default(), |v| v.collect());
     let extended_regexp = matches.get_flag("extended_regexp");
     let fixed_strings = matches.get_flag("fixed_strings");
+    let basic_regexp = matches.get_flag("basic_regexp");
     let perl_regexp = matches.get_flag("perl_regexp");
     let regexp = matches.get_many::<String>("regexp").unwrap_or_default();
     let file_pattern = matches
@@ -197,6 +198,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     #[cfg(windows)]
     let binary = matches.get_flag("binary");
 
+    let matcher_mode_count = [extended_regexp, fixed_strings, basic_regexp, perl_regexp]
+        .into_iter()
+        .filter(|matched| *matched)
+        .count();
+    if matcher_mode_count > 1 {
+        return Err(USimpleError::new(
+            2,
+            "conflicting matchers specified".to_string(),
+        ));
+    }
+
     // With -e/-f given, ALL positionals are files.
     let has_explicit_patterns = regexp.len() != 0 || file_pattern.len() != 0;
     let (positional_pattern, file_args) = if has_explicit_patterns {
@@ -461,32 +473,28 @@ pub fn uu_app() -> Command {
                 .short('E')
                 .long("extended-regexp")
                 .help("PATTERNS are extended regular expressions")
-                .action(ArgAction::SetTrue)
-                .overrides_with_all(["basic_regexp", "fixed_strings", "perl_regexp"]),
+                .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new("fixed_strings")
                 .short('F')
                 .long("fixed-strings")
                 .help("PATTERNS are strings")
-                .action(ArgAction::SetTrue)
-                .overrides_with_all(["basic_regexp", "extended_regexp", "perl_regexp"]),
+                .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new("basic_regexp")
                 .short('G')
                 .long("basic-regexp")
                 .help("PATTERNS are basic regular expressions")
-                .action(ArgAction::SetTrue)
-                .overrides_with_all(["extended_regexp", "fixed_strings", "perl_regexp"]),
+                .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new("perl_regexp")
                 .short('P')
                 .long("perl-regexp")
                 .help("PATTERNS are Perl regular expressions")
-                .action(ArgAction::SetTrue)
-                .overrides_with_all(["basic_regexp", "extended_regexp", "fixed_strings"]),
+                .action(ArgAction::SetTrue),
         )
         .arg(
             Arg::new("regexp")
diff --git a/tests/test_grep.rs b/tests/test_grep.rs
index 2c16db4..59aca3b 100644
--- a/tests/test_grep.rs
+++ b/tests/test_grep.rs
@@ -165,6 +165,41 @@ fn fixed_string_is_literal() {
         .stdout_only("hi\nHI\n");
 }
 
+#[test]
+fn conflicting_matcher_flags_are_rejected() {
+    let cases: &[&[&str]] = &[
+        &["-e", ".", "-F", "-G"],
+        &["-e", ".", "-F", "-E"],
+        &["-e", ".", "-E", "-G"],
+        &["-e", ".", "-G", "-E"],
+        &["-e", ".", "-P", "-F"],
+        &["-e", ".", "-P", "-E"],
+        &["-e", ".", "-P", "-G"],
+        &["-e", ".", "-G", "-F", "-E"],
+        &["-e", ".", "--fixed-strings", "--basic-regexp"],
+    ];
+
+    for args in cases {
+        let (_s, mut c) = ucmd();
+        c.args(args)
+            .fails_with_code(2)
+            .stderr_contains("conflicting matchers specified")
+            .no_stdout();
+    }
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-e", ".", "-F", "-F"])
+        .pipe_in("abc\n")
+        .fails_with_code(1)
+        .no_stdout();
+
+    let (_s, mut c) = ucmd();
+    c.args(&["-e", ".", "-E", "-E"])
+        .pipe_in("abc\n")
+        .succeeds()
+        .stdout_only("abc\n");
+}
+
 #[test]
 fn pcre_features() {
     let (_s, mut c) = ucmd();
@@ -197,14 +232,12 @@ fn perl_regexp_rejects_multiple_patterns() {
     // Two separate -e flags.
     let (_s, mut c) = ucmd();
     c.args(&["-P", "-e", "foo", "-e", "bar"])
-        .pipe_in("foo\nbar\n")
         .fails_with_code(2)
         .stderr_contains("the -P option only supports a single pattern");
 
     // A newline inside the pattern string is split into multiple patterns.
     let (_s, mut c) = ucmd();
     c.args(&["-P", "-e", "foo\nbar"])
-        .pipe_in("foo\nbar\n")
         .fails_with_code(2)
         .stderr_contains("the -P option only supports a single pattern");