3 files changed, 18 insertions, 2 deletions
diff --git a/spec/ruby/core/string/unpack/shared/basic.rb b/spec/ruby/core/string/unpack/shared/basic.rb
index bb5302edc5..734630bda0 100644
--- a/spec/ruby/core/string/unpack/shared/basic.rb
+++ b/spec/ruby/core/string/unpack/shared/basic.rb
@@ -8,6 +8,22 @@ describe :string_unpack_basic, shared: true do
     d.should_receive(:to_str).and_return("a"+unpack_format)
     "abc".unpack(d).should be_an_instance_of(Array)
   end
+
+  ruby_version_is ""..."3.3" do
+    it "warns about using an unknown directive" do
+      -> { "abcdefgh".unpack("a R" + unpack_format) }.should complain(/unknown unpack directive 'R' in 'a R#{unpack_format}'/)
+      -> { "abcdefgh".unpack("a 0" + unpack_format) }.should complain(/unknown unpack directive '0' in 'a 0#{unpack_format}'/)
+      -> { "abcdefgh".unpack("a :" + unpack_format) }.should complain(/unknown unpack directive ':' in 'a :#{unpack_format}'/)
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises ArgumentError when a directive is unknown" do
+      -> { "abcdefgh".unpack("a K" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive 'K' in 'a K#{unpack_format}'")
+      -> { "abcdefgh".unpack("a 0" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive '0' in 'a 0#{unpack_format}'")
+      -> { "abcdefgh".unpack("a :" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive ':' in 'a :#{unpack_format}'")
+    end
+  end
 end
 
 describe :string_unpack_no_platform, shared: true do
diff --git a/spec/ruby/core/string/unpack/shared/float.rb b/spec/ruby/core/string/unpack/shared/float.rb
index 93282bf4c9..b31c2c8bdc 100644
--- a/spec/ruby/core/string/unpack/shared/float.rb
+++ b/spec/ruby/core/string/unpack/shared/float.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :string_unpack_float_le, shared: true do
   it "decodes one float for a single format character" do
diff --git a/spec/ruby/core/string/unpack/shared/integer.rb b/spec/ruby/core/string/unpack/shared/integer.rb
index d71a2cf00d..d3934753ba 100644
--- a/spec/ruby/core/string/unpack/shared/integer.rb
+++ b/spec/ruby/core/string/unpack/shared/integer.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :string_unpack_16bit_le, shared: true do
   it "decodes one short for a single format character" do