diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 5d2bde7bf0..cf37d3eab4 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -1618,6 +1618,9 @@ on_request: installed_on_request?, options:)
 
     invalid_licenses = []
     forbidden_licenses = forbidden_licenses.split.each_with_object({}) do |license, hash|
+      license_sym = license.to_sym
+      license = license_sym if SPDX::ALLOWED_LICENSE_SYMBOLS.include?(license_sym)
+
       unless SPDX.valid_license?(license)
         invalid_licenses << license
         next
diff --git a/Library/Homebrew/test/formula_installer_spec.rb b/Library/Homebrew/test/formula_installer_spec.rb
index d0b079efcf..a1cd97dc02 100644
--- a/Library/Homebrew/test/formula_installer_spec.rb
+++ b/Library/Homebrew/test/formula_installer_spec.rb
@@ -255,6 +255,28 @@ RSpec.describe FormulaInstaller do
         fi.forbidden_license_check
       end.to raise_error(CannotInstallFormulaError, /dependency on #{dep_name} where all/)
     end
+
+    it "raises on forbidden symbol license on formula" do
+      ENV["HOMEBREW_FORBIDDEN_LICENSES"] = "public_domain"
+
+      f_name = "homebrew-forbidden-license"
+      f_path = CoreTap.instance.new_formula_path(f_name)
+      f_path.write <<~RUBY
+        class #{Formulary.class_s(f_name)} < Formula
+          url "foo"
+          version "0.1"
+          license :public_domain
+        end
+      RUBY
+      Formulary.cache.delete(f_path)
+
+      f = Formulary.factory(f_name)
+      fi = described_class.new(f)
+
+      expect do
+        fi.forbidden_license_check
+      end.to raise_error(CannotInstallFormulaError, /#{f_name}'s licenses are all forbidden/)
+    end
   end
 
   describe "#forbidden_tap_check" do
diff --git a/Library/Homebrew/utils/spdx.rb b/Library/Homebrew/utils/spdx.rb
index 7b8e69e865..96c95aba7b 100644
--- a/Library/Homebrew/utils/spdx.rb
+++ b/Library/Homebrew/utils/spdx.rb
@@ -229,13 +229,13 @@ module SPDX
   end
 
   sig {
-    params(license_expression: T.any(String, Symbol, T::Hash[Symbol, T.untyped]),
-           forbidden_licenses: T::Hash[Symbol, T.untyped]).returns(T::Boolean)
+    params(license_expression: T.any(String, Symbol, T::Hash[T.any(Symbol, String), T.untyped]),
+           forbidden_licenses: T::Hash[T.any(Symbol, String), T.untyped]).returns(T::Boolean)
   }
   def licenses_forbid_installation?(license_expression, forbidden_licenses)
     case license_expression
     when String, Symbol
-      forbidden_licenses_include? license_expression.to_s, forbidden_licenses
+      forbidden_licenses_include? license_expression, forbidden_licenses
     when Hash
       key = license_expression.keys.first
       return false if key.nil?