diff --git a/src/bootstrap/defaults/bootstrap.compiler.toml b/src/bootstrap/defaults/bootstrap.compiler.toml
index 9dcb20ed48323..f95006b5e9322 100644
--- a/src/bootstrap/defaults/bootstrap.compiler.toml
+++ b/src/bootstrap/defaults/bootstrap.compiler.toml
@@ -25,6 +25,8 @@ frame-pointers = true
 # e.g. check that it builds locally and check the baseline behavior of a
 # compiler built from latest `master` commit.
 download-rustc = false
+# Don't fail compilation when there are warnings.
+deny-warnings = false
 
 [llvm]
 # Having this set to true disrupts compiler development workflows for people who use `llvm.download-ci-llvm = true`
diff --git a/src/bootstrap/defaults/bootstrap.dist.toml b/src/bootstrap/defaults/bootstrap.dist.toml
index bb0592ce947ab..b7b5d564f14bb 100644
--- a/src/bootstrap/defaults/bootstrap.dist.toml
+++ b/src/bootstrap/defaults/bootstrap.dist.toml
@@ -24,6 +24,8 @@ channel = "auto-detect"
 download-rustc = false
 # Build the llvm-bitcode-linker
 llvm-bitcode-linker = true
+# Fail compilation when there are warnings.
+deny-warnings = true
 
 [dist]
 # Use better compression when preparing tarballs.
diff --git a/src/bootstrap/defaults/bootstrap.library.toml b/src/bootstrap/defaults/bootstrap.library.toml
index 3f811402b26ff..a4665a40d428b 100644
--- a/src/bootstrap/defaults/bootstrap.library.toml
+++ b/src/bootstrap/defaults/bootstrap.library.toml
@@ -14,6 +14,8 @@ lto = "off"
 # library development by skipping compiler builds.
 # FIXME: download-rustc is currently broken: https://github.com/rust-lang/rust/issues/142505
 download-rustc = false
+# Don't fail compilation when there are warnings.
+deny-warnings = false
 
 [llvm]
 # Will download LLVM from CI if available on your platform.
diff --git a/src/bootstrap/defaults/bootstrap.tools.toml b/src/bootstrap/defaults/bootstrap.tools.toml
index 5abe636bd9683..423ad1a395939 100644
--- a/src/bootstrap/defaults/bootstrap.tools.toml
+++ b/src/bootstrap/defaults/bootstrap.tools.toml
@@ -6,6 +6,8 @@ incremental = true
 # Most commonly, tools contributors do not need to modify the compiler, so
 # downloading a CI rustc is a good default for tools profile.
 download-rustc = "if-unchanged"
+# Don't fail compilation when there are warnings.
+deny-warnings = false
 
 [build]
 # cargo and clippy tests don't pass on stage 1