diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 5d53d2f3..e97e28a3 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -32,9 +32,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macOS-latest, windows-latest]
+        include:
+          - os: ubuntu-latest
+            cc: clang
+            cxx: clang++
+          - os: macOS-latest
+          - os: windows-latest
     runs-on: ${{ matrix.os }}
-
+    env:
+      CC: ${{ matrix.cc }}
+      CXX: ${{ matrix.cxx }}
 
     steps:
     - uses: actions/checkout@v2
diff --git a/Fleece/Support/Backtrace+capture-posix.cc b/Fleece/Support/Backtrace+capture-posix.cc
index 6b2022e1..775628af 100644
--- a/Fleece/Support/Backtrace+capture-posix.cc
+++ b/Fleece/Support/Backtrace+capture-posix.cc
@@ -199,7 +199,8 @@ namespace signal_safe {
 #endif
 
         if ( fd != -1 ) write(fd, str, n ? n : strlen(str));
-        write(STDERR_FILENO, str, n ? n : strlen(str));
+        if (getenv("CBL_BACKTRACE_TO_STDERR") != nullptr)
+            write(STDERR_FILENO, str, n ? n : strlen(str));
 
 #ifdef __clang__
 #    pragma clang diagnostic pop
diff --git a/Tests/SupportTests.cc b/Tests/SupportTests.cc
index a27f368b..c1e3ccb4 100644
--- a/Tests/SupportTests.cc
+++ b/Tests/SupportTests.cc
@@ -409,6 +409,11 @@ namespace test::backtrace {
 TEST_CASE("Backtrace crash", "[.BacktraceManual]") {
     // Since this test crashes the process intentionally,
     // It will fail and require manual inspection of stderr
+#ifdef _MSC_VER
+    SetEnvironmentVariable("CBL_BACKTRACE_TO_STDERR", "1");
+#else
+    setenv("CBL_BACKTRACE_TO_STDERR", "1", 1);
+#endif
     test::backtrace::crashOnPurpose();
 }