diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9f43306..03b17e0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.51.0, 1.50.0]
+        rust: [nightly, beta, stable, 1.52.0]
     steps:
       - uses: actions/checkout@v2
       - uses: dtolnay/rust-toolchain@master
@@ -22,6 +22,21 @@ jobs:
       - run: cargo test
       - run: cargo check --no-default-features
       - run: cargo check --features backtrace
+
+  build:
+    name: Rust ${{matrix.rust}}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        rust: [1.51.0, 1.50.0]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{matrix.rust}}
+      - run: cargo check --no-default-features
+      - run: cargo check --features backtrace
         if: matrix.rust != '1.50.0'
 
   backtrace:
diff --git a/src/lib.rs b/src/lib.rs
index b227eef..9be302b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -622,21 +622,21 @@ pub mod private {
 
     #[doc(hidden)]
     #[cold]
-    pub fn format_err<M>(message: M, args: Arguments) -> Error
+    pub fn format_err<M>(_message: M, args: Arguments) -> Error
     where
         M: Display + Debug + Send + Sync + 'static,
     {
         #[cfg(anyhow_no_fmt_arguments_as_str)]
-        let has_interpolated_format_args = false;
+        let fmt_arguments_as_str = Some(_message);
         #[cfg(not(anyhow_no_fmt_arguments_as_str))]
-        let has_interpolated_format_args = args.as_str().is_none();
+        let fmt_arguments_as_str = args.as_str();
 
-        if has_interpolated_format_args {
-            // anyhow!("interpolate {var}"), can downcast to String
-            Error::msg(fmt::format(args))
-        } else {
+        if let Some(message) = fmt_arguments_as_str {
             // anyhow!("literal"), can downcast to &'static str
             Error::msg(message)
+        } else {
+            // anyhow!("interpolate {var}"), can downcast to String
+            Error::msg(fmt::format(args))
         }
     }
 }
diff --git a/tests/test_macros.rs b/tests/test_macros.rs
index b08db97..4cbb580 100644
--- a/tests/test_macros.rs
+++ b/tests/test_macros.rs
@@ -56,3 +56,9 @@ fn test_temporaries() {
         future::ready(anyhow!("...")).await;
     });
 }
+
+#[test]
+fn test_brace_escape() {
+    let err = anyhow!("unterminated ${{..}} expression");
+    assert_eq!("unterminated ${..} expression", err.to_string());
+}