diff --git a/build_tests/simple/cache_debugging.rb b/build_tests/simple/cache_debugging.rb
index 4a7c8ba..77a381d 100644
--- a/build_tests/simple/cache_debugging.rb
+++ b/build_tests/simple/cache_debugging.rb
@@ -4,7 +4,7 @@ class DebugBuilder < Rscons::Builder
       finalize_command
     else
       @command = %W[gcc -c -o #{@target} #{@sources.first}]
-      if ENV["command_change"] == "command_change"
+      if ENV["test"] == "command_change"
         @command += %w[-Wall]
       end
       if ENV["test"] == "new_dep"
diff --git a/lib/rscons/cli.rb b/lib/rscons/cli.rb
index 29f9b60..21b4de1 100644
--- a/lib/rscons/cli.rb
+++ b/lib/rscons/cli.rb
@@ -41,6 +41,7 @@ module Rscons
           end
           unless valid_arg
             $stderr.puts "Invalid task '#{task}' argument '#{argv[0].split("=").first}'"
+            $stderr.puts usage
             exit 2
           end
         else
diff --git a/spec/build_tests_spec.rb b/spec/build_tests_spec.rb
index 89fea88..89eab92 100644
--- a/spec/build_tests_spec.rb
+++ b/spec/build_tests_spec.rb
@@ -89,7 +89,7 @@ describe Rscons do
   end
 
   def run_rscons(options = {})
-    args = options[:args] || []
+    args = Array(options[:args]) || []
     if ENV["dist_specs"]
       exe = "#{@owd}/test/rscons.rb"
     else
@@ -1754,10 +1754,10 @@ EOF
       expect(result.status).to_not eq 0
     end
 
-    it "outputs an error for an unknown operation" do
+    it "outputs an error for an unknown task" do
       test_dir "simple"
       result = run_rscons(args: "unknownop")
-      expect(result.stderr).to match /Unknown operation: unknownop/
+      expect(result.stderr).to match /Task 'unknownop' not found/
       expect(result.status).to_not eq 0
     end
 
@@ -1774,7 +1774,7 @@ EOF
       test_dir "simple"
       result = run_rscons(args: %w[configure --xyz])
       expect(result.stderr).to_not match /Traceback/
-      expect(result.stderr).to match /invalid option.*--xyz/
+      expect(result.stderr).to match /Invalid task 'configure' argument.*--xyz/
       expect(result.stderr).to match /Usage:/
       expect(result.status).to_not eq 0
     end
@@ -2424,16 +2424,6 @@ EOF
       expect(result.stderr).to eq ""
       expect(result.stdout).to match /gcc.*-o.*simple/
     end
-
-    it "prints operation start time" do
-      test_dir("simple")
-      result = run_rscons(args: %w[-v])
-      expect(result.stderr).to eq ""
-      expect(result.stdout).to match /Starting 'configure' at/
-      expect(result.stdout).to match /Starting 'build' at/
-      expect(result.stdout).to match /'build' complete at/
-      expect(result.stdout).to_not match /'configure' complete at/
-    end
   end
 
   context "direct mode" do