diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d0e1175..fc64451d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,8 @@ Bug fixes:
   Fix stdin detection when using PowerShell in UNIX environments.
 * [BUG #1866](https://github.com/BurntSushi/ripgrep/issues/1866#issuecomment-841635553):
   Fix bug when computing column numbers in `--vimgrep` mode.
+* [BUG #1878](https://github.com/BurntSushi/ripgrep/issues/1878):
+  Fix bug where `\A` could produce unanchored matches in multiline search.
 
 
 12.1.1 (2020-05-29)
diff --git a/crates/regex/src/non_matching.rs b/crates/regex/src/non_matching.rs
index 2270f94d..e2e0755b 100644
--- a/crates/regex/src/non_matching.rs
+++ b/crates/regex/src/non_matching.rs
@@ -13,7 +13,10 @@ pub fn non_matching_bytes(expr: &Hir) -> ByteSet {
 /// the given expression.
 fn remove_matching_bytes(expr: &Hir, set: &mut ByteSet) {
     match *expr.kind() {
-        HirKind::Empty | HirKind::Anchor(_) | HirKind::WordBoundary(_) => {}
+        HirKind::Empty | HirKind::WordBoundary(_) => {}
+        HirKind::Anchor(_) => {
+            set.remove(b'\n');
+        }
         HirKind::Literal(hir::Literal::Unicode(c)) => {
             for &b in c.encode_utf8(&mut [0; 4]).as_bytes() {
                 set.remove(b);
diff --git a/tests/regression.rs b/tests/regression.rs
index 2935a43e..9aba2746 100644
--- a/tests/regression.rs
+++ b/tests/regression.rs
@@ -882,3 +882,26 @@ test:3:5:foo quux
 ";
     eqnice!(expected, cmd.stdout());
 });
+
+rgtest!(r1878, |dir: Dir, _: TestCommand| {
+    dir.create("test", "a\nbaz\nabc\n");
+
+    // Since ripgrep enables (?m) by default, '^' will match at the beginning
+    // of a line, even when -U/--multiline is used.
+    let args = &["-U", "--no-mmap", r"^baz", "test"];
+    eqnice!("baz\n", dir.command().args(args).stdout());
+    let args = &["-U", "--mmap", r"^baz", "test"];
+    eqnice!("baz\n", dir.command().args(args).stdout());
+
+    // But when (?-m) is disabled, or when \A is used, then there should be no
+    // matches that aren't anchored to the beginning of the file.
+    let args = &["-U", "--no-mmap", r"(?-m)^baz", "test"];
+    dir.command().args(args).assert_err();
+    let args = &["-U", "--mmap", r"(?-m)^baz", "test"];
+    dir.command().args(args).assert_err();
+
+    let args = &["-U", "--no-mmap", r"\Abaz", "test"];
+    dir.command().args(args).assert_err();
+    let args = &["-U", "--mmap", r"\Abaz", "test"];
+    dir.command().args(args).assert_err();
+});