diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..c0f8b3e
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+3.4.0-preview2
diff --git a/ext/vernier/vernier.cc b/ext/vernier/vernier.cc
index ba4e880..7618016 100644
--- a/ext/vernier/vernier.cc
+++ b/ext/vernier/vernier.cc
@@ -1989,7 +1989,7 @@ collector_start(VALUE self) {
     auto *collector = get_collector(self);
 
     if (!collector->start()) {
-        rb_raise(rb_eRuntimeError, "already running");
+        rb_raise(rb_eRuntimeError, "collector already running");
     }
 
     return Qtrue;
diff --git a/lib/vernier.rb b/lib/vernier.rb
index 27aae7b..cb08572 100644
--- a/lib/vernier.rb
+++ b/lib/vernier.rb
@@ -40,7 +40,7 @@ def self.start_profile(mode: :wall, **collector_options)
       @collector.stop
       @collector = nil
 
-      raise "Profile already started, stopping..."
+      raise "profile already started, stopping..."
     end
 
     @collector = Vernier::Collector.new(mode, collector_options)
@@ -48,7 +48,7 @@ def self.start_profile(mode: :wall, **collector_options)
   end
 
   def self.stop_profile
-    raise "No profile started" unless @collector
+    raise "profile not started" unless @collector
 
     result = @collector.stop
     @collector = nil
diff --git a/lib/vernier/collector.rb b/lib/vernier/collector.rb
index 59aa21c..d9e695b 100644
--- a/lib/vernier/collector.rb
+++ b/lib/vernier/collector.rb
@@ -32,7 +32,7 @@ def initialize(mode, options = {})
       when :rails, :activesupport
         @hooks << Vernier::Hooks::ActiveSupport.new(self)
       else
-        warn "Unknown hook: #{hook.inspect}"
+        warn "unknown hook: #{hook.inspect}"
       end
     end
 
diff --git a/test/test_time_collector.rb b/test/test_time_collector.rb
index 4058121..27f14c0 100644
--- a/test/test_time_collector.rb
+++ b/test/test_time_collector.rb
@@ -247,14 +247,14 @@ def test_multiple_starts
       Vernier.start_profile(interval: SAMPLE_SCALE_INTERVAL)
       Vernier.start_profile(interval: SAMPLE_SCALE_INTERVAL)
     end
-    assert_equal "Profile already started, stopping...", error.message
+    assert_equal "profile already started, stopping...", error.message
   end
 
   def test_stop_without_start
     error = assert_raises("No trace started") do
       Vernier.stop_profile
     end
-    assert_equal "No profile started", error.message
+    assert_equal "profile not started", error.message
   end
 
   def test_includes_options_in_result_meta