If for some reason you need to disable automatic conversion of underscores to hyphens, set the parameter `convert_underscores` of `Header` to `False`:

{* ../../docs_src/header_params/tutorial002_an_py310.py hl[10] *}

/// warning

Before setting `convert_underscores` to `False`, bear in mind that some HTTP proxies and servers disallow the usage of headers with underscores.

///

## Duplicate headers { #duplicate-headers }

            "msg": "Extra inputs are not permitted",
            "input": "plumbus",
        }
    ]
}
```

## Disable Convert Underscores { #disable-convert-underscores }

The same way as with regular header parameters, when you have underscore characters in the parameter names, they are **automatically converted to hyphens**.

import (
	"strconv"

	"github.com/minio/minio/internal/bucket/lifecycle"
)

//go:generate stringer -type lcEventSrc -trimprefix lcEventSrc_ $GOFILE
type lcEventSrc uint8

//nolint:staticcheck,revive // Underscores are used here to indicate where common prefix ends and the enumeration name begins
const (
	lcEventSrc_None lcEventSrc = iota
	lcEventSrc_Heal
	lcEventSrc_Scanner
	lcEventSrc_Decom
	lcEventSrc_Rebal

  static class EmptyTest {}

  static class EmptyTests {}

  static class EmptyTestSuite {}

  static class Foo {}

  @SuppressWarnings("IdentifierName") // We're testing that we ignore classes with underscores.
  static class Foo_Bar {}

  public static class PublicFoo {}

  static class FooTest {
    @SuppressWarnings("unused") // accessed reflectively
    public void testPublic() {}

        value = "${123}";
        assertEquals("numeric", ResourceUtil.resolve(value));

        // Test with underscores in property names
        System.setProperty("test_var", "underscore");
        value = "${test_var}";
        assertEquals("underscore", ResourceUtil.resolve(value));

        // Clean up test properties
        System.clearProperty("var1");
        System.clearProperty("var2");

     * <p>ASCII characters in the part are expected to be valid per RFC 1035, with underscore also
     * being allowed due to widespread practice.
     */

    String asciiChars = CharMatcher.ascii().retainFrom(part);

    if (!PART_CHAR_MATCHER.matchesAllOf(asciiChars)) {
      return false;
    }

    // No initial or final dashes or underscores.

    if (DASH_MATCHER.matches(part.charAt(0))

        this.logLevel = logLevel;
        return this;
    }

    /**
     * Sets the log suffix for this job execution.
     * The suffix is trimmed and whitespace is replaced with underscores.
     *
     * @param logSuffix the suffix to append to log file names
     * @return this ExecJob instance for method chaining
     */
    public ExecJob logSuffix(final String logSuffix) {

        if (options.sessionId != null) {
            options.sessionId = options.sessionId.replaceAll("-", "_");
        }

        // Check that sessionId was sanitized (hyphens replaced with underscores)
        assertEquals("test_session_123", options.sessionId);
    }

    public void test_process_withPropertiesPath() throws Exception {
        // Test that properties path is properly handled

        }
        return value;
    }

    /**
     * Replaces special characters in a string with underscores for group names.
     *
     * @param value the string to process
     * @return the string with special characters replaced by underscores
     */
    protected String replaceWithUnderscores(final String value) {
        return value.replaceAll("[/\\\\\\[\\]:;|=,+\\*?<>]", "_");

 *  New: OkHttp includes a user-agent by default, like `okhttp/2.1.0-RC1`.
 *  Fix: Handle response code `308 Permanent Redirect`.
 *  Fix: Don't skip the callback if a call is canceled.
 *  Fix: Permit hostnames with underscores.
 *  Fix: Permit overriding the content-type in `OkApacheClient`.
 *  Fix: Use the socket factory for direct connections.
 *  Fix: Honor `OkUrlFactory` APIs that disable redirects.