diff --git a/build_tests/simple/cache_debugging.rb b/build_tests/simple/cache_debugging.rb
index 84330e9..cd6a00e 100644
--- a/build_tests/simple/cache_debugging.rb
+++ b/build_tests/simple/cache_debugging.rb
@@ -2,17 +2,17 @@ class DebugBuilder < Rscons::Builder
   def run(options)
     target, sources, cache, env, vars = options.values_at(:target, :sources, :cache, :env, :vars)
     command = %W[gcc -c -o #{target} #{sources.first}]
-    if ENV["command_change"]
+    if Rscons.vars["command_change"]
       command += %w[-Wall]
     end
-    if ENV["new_dep"]
+    if Rscons.vars["new_dep"]
       sources += ["extra"]
     end
-    if ENV["strict_deps1"]
+    if Rscons.vars["strict_deps1"]
       sources += ["extra"]
       strict_deps = true
     end
-    if ENV["strict_deps2"]
+    if Rscons.vars["strict_deps2"]
       sources = ["extra"] + sources
       strict_deps = true
     end
@@ -27,7 +27,7 @@ end
 
 Rscons::Environment.new do |env|
   env.add_builder(DebugBuilder.new)
-  if ENV["new_user_dep"]
+  if Rscons.vars["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 294b3fb..5691fc1 100644
--- a/lib/rscons.rb
+++ b/lib/rscons.rb
@@ -55,6 +55,11 @@ module Rscons
     #   Whether to output ANSI color escape sequences.
     attr_accessor :do_ansi_color
 
+    # @since 1.16.0
+    # @return [VarSet]
+    #   Access any variables set on the rscons command-line.
+    attr_reader :vars
+
     # Remove all generated files.
     #
     # @return [void]
@@ -232,6 +237,7 @@ module Rscons
   end
 
   @n_threads = determine_n_threads
+  @vars = VarSet.new
 
 end
 
diff --git a/lib/rscons/cli.rb b/lib/rscons/cli.rb
index 1d5f5d5..bcdbb73 100644
--- a/lib/rscons/cli.rb
+++ b/lib/rscons/cli.rb
@@ -60,6 +60,12 @@ module Rscons
 
         end.parse!(argv)
 
+        argv.each do |arg|
+          if arg =~ /^([^=]+)=(.*)$/
+            Rscons.vars[$1] = $2
+          end
+        end
+
         if rsconsfile
           unless File.exists?(rsconsfile)
             $stderr.puts "Cannot read #{rsconsfile}"
diff --git a/spec/build_tests_spec.rb b/spec/build_tests_spec.rb
index 10e3a2a..f2f6489 100644
--- a/spec/build_tests_spec.rb
+++ b/spec/build_tests_spec.rb
@@ -1300,28 +1300,28 @@ EOF
       it "prints a message when the command has changed" do
         test_dir("simple")
         result = run_test(rsconsfile: "cache_debugging.rb")
-        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["command_change"] = "yes"])
+        result = run_test(rsconsfile: "cache_debugging.rb", rscons_args: %w[command_change=yes])
         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_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["strict_deps1"] = "yes"])
-        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["strict_deps2"] = "yes"])
+        result = run_test(rsconsfile: "cache_debugging.rb", rscons_args: %w[strict_deps1=yes])
+        result = run_test(rsconsfile: "cache_debugging.rb", rscons_args: %w[strict_deps2=yes])
         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
 
       it "prints a message when there is a new dependency" do
         test_dir("simple")
         result = run_test(rsconsfile: "cache_debugging.rb")
-        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["new_dep"] = "yes"])
+        result = run_test(rsconsfile: "cache_debugging.rb", rscons_args: %w[new_dep=yes])
         expect(result.stdout).to match /Target foo\.o needs rebuilding because there are new dependencies/
       end
 
       it "prints a message when there is a new user-specified dependency" do
         test_dir("simple")
         result = run_test(rsconsfile: "cache_debugging.rb")
-        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["new_user_dep"] = "yes"])
+        result = run_test(rsconsfile: "cache_debugging.rb", rscons_args: %w[new_user_dep=yes])
         expect(result.stdout).to match /Target foo\.o needs rebuilding because the set of user-specified dependency files has changed/
       end