diff --git a/Cargo.toml b/Cargo.toml
index af73a7af31c..b6e1cdf5ca8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -57,3 +57,6 @@ default = ["stack-cache"]
 # Will be enabled on CI via `--all-features`.
 expensive-debug-assertions = []
 stack-cache = []
+
+[profile.dev]
+opt-level = 2 # because it's too slow otherwise
diff --git a/ci.sh b/ci.sh
index e7c6ed833c6..05a3ee358ce 100755
--- a/ci.sh
+++ b/ci.sh
@@ -3,7 +3,7 @@ set -euo pipefail
 set -x
 
 # Determine configuration
-export RUSTFLAGS="-D warnings"
+export RUSTFLAGS="-D warnings -C debug-assertions -C debuginfo=1"
 export CARGO_INCREMENTAL=0
 export CARGO_EXTRA_FLAGS="--all-features" # in particular, expensive-debug-assertions
 
diff --git a/miri b/miri
index f0d92b6a2b5..a1931485f69 100755
--- a/miri
+++ b/miri
@@ -108,9 +108,7 @@ if [ -z "$CARGO_TARGET_DIR" ]; then
     export CARGO_TARGET_DIR="$MIRIDIR/target"
 fi
 # We set the rpath so that Miri finds the private rustc libraries it needs.
-# We enable debug-assertions to get tracing.
-# We enable line-only debuginfo for backtraces.
-export RUSTFLAGS="-C link-args=-Wl,-rpath,$LIBDIR -C debug-assertions -C debuginfo=1 $RUSTFLAGS"
+export RUSTFLAGS="-C link-args=-Wl,-rpath,$LIBDIR $RUSTFLAGS"
 # Determine flags passed to all cargo invocations.
 # This is a bit more annoying that one would hope due to
 # <https://github.com/rust-lang/cargo/issues/6992>.