diff --git a/build_tests/simple/cache_debugging.rb b/build_tests/simple/cache_debugging.rb
index fc0699d..4a7c8ba 100644
--- a/build_tests/simple/cache_debugging.rb
+++ b/build_tests/simple/cache_debugging.rb
@@ -4,17 +4,17 @@ class DebugBuilder < Rscons::Builder
       finalize_command
     else
       @command = %W[gcc -c -o #{@target} #{@sources.first}]
-      if Rscons.vars["command_change"]
+      if ENV["command_change"] == "command_change"
         @command += %w[-Wall]
       end
-      if Rscons.vars["new_dep"]
+      if ENV["test"] == "new_dep"
         @sources += ["extra"]
       end
-      if Rscons.vars["strict_deps1"]
+      if ENV["test"] == "strict_deps1"
         @sources += ["extra"]
         strict_deps = true
       end
-      if Rscons.vars["strict_deps2"]
+      if ENV["test"] == "strict_deps2"
         @sources = ["extra"] + @sources
         strict_deps = true
       end
@@ -30,7 +30,7 @@ end
 default do
   Environment.new do |env|
     env.add_builder(DebugBuilder)
-    if Rscons.vars["new_user_dep"]
+    if ENV["test"] == "new_user_dep"
       env.depends("foo.o", "new_dep")
     end
     env.DebugBuilder("foo.o", "simple.c")
diff --git a/lib/rscons.rb b/lib/rscons.rb
index c11e645..bfd14a1 100644
--- a/lib/rscons.rb
+++ b/lib/rscons.rb
@@ -50,13 +50,6 @@ module Rscons
       @application ||= Application.new
     end
 
-    # Access any variables set on the rscons command-line.
-    #
-    # @return [VarSet]
-    def vars(*args)
-      application.vars(*args)
-    end
-
     # Return whether the given target is a phony target.
     #
     # @param target [Symbol, String] Target name.
diff --git a/lib/rscons/application.rb b/lib/rscons/application.rb
index 4ffa50d..0bec85f 100644
--- a/lib/rscons/application.rb
+++ b/lib/rscons/application.rb
@@ -21,16 +21,11 @@ module Rscons
     #   Whether to run verbosely.
     attr_accessor :verbose
 
-    # @return [VarSet]
-    #   Access any variables set on the rscons command-line.
-    attr_reader :vars
-
     # Create Application instance.
     def initialize
       @build_dir = ENV["RSCONS_BUILD_DIR"] || "build"
       ENV.delete("RSCONS_BUILD_DIR")
       @n_threads = Util.determine_n_threads
-      @vars = VarSet.new
       @build_step = 0
     end
 
diff --git a/lib/rscons/cli.rb b/lib/rscons/cli.rb
index 5f19d15..8604d29 100644
--- a/lib/rscons/cli.rb
+++ b/lib/rscons/cli.rb
@@ -111,14 +111,6 @@ module Rscons
 
       end.order!(argv)
 
-      # Set vars before loading the build script so the build script can
-      # refer to them.
-      argv.each do |arg|
-        if arg =~ /^([^=]+)=(.*)$/
-          Rscons.application.vars[$1] = $2
-        end
-      end
-
       # Find the build script.
       if rsconscript
         unless File.exists?(rsconscript)
diff --git a/spec/build_tests_spec.rb b/spec/build_tests_spec.rb
index 345c4a1..30a51e5 100644
--- a/spec/build_tests_spec.rb
+++ b/spec/build_tests_spec.rb
@@ -1544,16 +1544,19 @@ EOF
         test_dir("simple")
         result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
-        result = run_rscons(args: %w[-f cache_debugging.rb build command_change=yes])
+        passenv["test"] = "command_change"
+        result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
         expect(result.stdout).to match /Target foo\.o needs rebuilding because the command used to build it has changed/
       end
 
       it "prints a message when strict_deps is in use and the set of dependencies does not match" do
         test_dir("simple")
-        result = run_rscons(args: %w[-f cache_debugging.rb build strict_deps1=yes])
+        passenv["test"] = "strict_deps1"
+        result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
-        result = run_rscons(args: %w[-f cache_debugging.rb build strict_deps2=yes])
+        passenv["test"] = "strict_deps2"
+        result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
         expect(result.stdout).to match /Target foo\.o needs rebuilding because the :strict_deps option is given and the set of dependencies does not match the previous set of dependencies/
       end
@@ -1562,7 +1565,8 @@ EOF
         test_dir("simple")
         result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
-        result = run_rscons(args: %w[-f cache_debugging.rb build new_dep=yes])
+        passenv["test"] = "new_dep"
+        result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
         expect(result.stdout).to match /Target foo\.o needs rebuilding because there are new dependencies/
       end
@@ -1571,7 +1575,8 @@ EOF
         test_dir("simple")
         result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
-        result = run_rscons(args: %w[-f cache_debugging.rb build new_user_dep=yes])
+        passenv["test"] = "new_user_dep"
+        result = run_rscons(args: %w[-f cache_debugging.rb])
         expect(result.stderr).to eq ""
         expect(result.stdout).to match /Target foo\.o needs rebuilding because the set of user-specified dependency files has changed/
       end
@@ -2331,7 +2336,7 @@ EOF
     it "does everything" do
       test_dir "configure"
       create_exe "pkg-config", "echo '-DMYPACKAGE'"
-      result = run_rscons(args: %w[-f everything.rb configure --build=bb --prefix=/my/prefix])
+      result = run_rscons(args: %w[-f everything.rb --build=bb configure --prefix=/my/prefix])
       expect(result.stderr).to eq ""
       expect(result.status).to eq 0
       expect(result.stdout).to match /Configuring configure test\.\.\./