diff --git a/Library/Homebrew/cli_parser.rb b/Library/Homebrew/cli_parser.rb
index f35328a574..5ed6e4bd85 100644
--- a/Library/Homebrew/cli_parser.rb
+++ b/Library/Homebrew/cli_parser.rb
@@ -234,7 +234,7 @@ module Homebrew
           next if violations.count < 2
 
           env_var_options = violations.select do |option|
-            @switch_sources[option_to_name(option)] == :env_var
+            @switch_sources[option_to_name(option)] == :env
           end
 
           select_cli_arg = violations.count - env_var_options.count == 1
diff --git a/Library/Homebrew/test/cli_parser_spec.rb b/Library/Homebrew/test/cli_parser_spec.rb
index c5c1f25764..c4b1dfe033 100644
--- a/Library/Homebrew/test/cli_parser_spec.rb
+++ b/Library/Homebrew/test/cli_parser_spec.rb
@@ -179,19 +179,19 @@ describe Homebrew::CLI::Parser do
     end
 
     it "prioritizes cli arguments over env vars when they conflict" do
-      allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_A").and_return("1")
-      allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_B").and_return("0")
       allow(ENV).to receive(:[])
+      allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_A").and_return("1")
+      allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_B").and_return(nil)
       parser.parse(["--switch-b"])
       expect(Homebrew.args.switch_a).to be_falsy
       expect(Homebrew.args).to be_switch_b
     end
 
     it "raises an exception on constraint violation when both are env vars" do
+      allow(ENV).to receive(:[])
       allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_A").and_return("1")
       allow(ENV).to receive(:[]).with("HOMEBREW_SWITCH_B").and_return("1")
-      allow(ENV).to receive(:[])
-      expect { parser.parse(["--switch-a", "--switch-b"]) }.to raise_error(Homebrew::CLI::OptionConflictError)
+      expect { parser.parse([]) }.to raise_error(Homebrew::CLI::OptionConflictError)
     end
   end