diff --git a/okhttp-tests/src/test/java/okhttp3/HeadersTest.java b/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
index e5dfaa3ca5a1..a431dbe124f5 100644
--- a/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
+++ b/okhttp-tests/src/test/java/okhttp3/HeadersTest.java
@@ -121,6 +121,25 @@ public final class HeadersTest {
     }
   }
 
+  @Test public void addUnsafeNonAsciiRejectsUnicodeName() {
+    try {
+      Headers headers = new Headers.Builder()
+          .addUnsafeNonAscii("héader1", "value1")
+          .build();
+      fail("Should have complained about invalid value");
+    } catch (IllegalArgumentException expected) {
+      assertEquals("Unexpected char 0xe9 at 1 in header name: héader1",
+          expected.getMessage());
+    }
+  }
+
+  @Test public void addUnsafeNonAsciiAcceptsUnicodeValue() {
+    Headers headers = new Headers.Builder()
+        .addUnsafeNonAscii("header1", "valué1")
+        .build();
+    assertEquals("header1: valué1\n", headers.toString());
+  }
+
   @Test public void ofThrowsOddNumberOfHeaders() {
     try {
       Headers.of("User-Agent", "OkHttp", "Content-Length");
diff --git a/okhttp/src/main/java/okhttp3/Headers.java b/okhttp/src/main/java/okhttp3/Headers.java
index f55b2979d2f0..73552fbee041 100644
--- a/okhttp/src/main/java/okhttp3/Headers.java
+++ b/okhttp/src/main/java/okhttp3/Headers.java
@@ -220,7 +220,8 @@ public static Headers of(String... namesAndValues) {
     for (int i = 0; i < namesAndValues.length; i += 2) {
       String name = namesAndValues[i];
       String value = namesAndValues[i + 1];
-      checkNameAndValue(name, value);
+      checkName(name);
+      checkValue(value, name);
     }
 
     return new Headers(namesAndValues);
@@ -241,7 +242,8 @@ public static Headers of(Map<String, String> headers) {
       }
       String name = header.getKey().trim();
       String value = header.getValue().trim();
-      checkNameAndValue(name, value);
+      checkName(name);
+      checkValue(value, name);
       namesAndValues[i] = name;
       namesAndValues[i + 1] = value;
       i += 2;
@@ -250,7 +252,7 @@ public static Headers of(Map<String, String> headers) {
     return new Headers(namesAndValues);
   }
 
-  static void checkNameAndValue(String name, String value) {
+  static void checkName(String name) {
     if (name == null) throw new NullPointerException("name == null");
     if (name.isEmpty()) throw new IllegalArgumentException("name is empty");
     for (int i = 0, length = name.length(); i < length; i++) {
@@ -260,6 +262,9 @@ static void checkNameAndValue(String name, String value) {
             "Unexpected char %#04x at %d in header name: %s", (int) c, i, name));
       }
     }
+  }
+
+  static void checkValue(String value, String name) {
     if (value == null) throw new NullPointerException("value for name " + name + " == null");
     for (int i = 0, length = value.length(); i < length; i++) {
       char c = value.charAt(i);
@@ -303,7 +308,17 @@ public Builder add(String line) {
      * Add a header with the specified name and value. Does validation of header names and values.
      */
     public Builder add(String name, String value) {
-      checkNameAndValue(name, value);
+      checkName(name);
+      checkValue(value, name);
+      return addLenient(name, value);
+    }
+
+    /**
+     * Add a header with the specified name and value. Does validation of header names, allowing
+     * non-ASCII values.
+     */
+    public Builder addUnsafeNonAscii(String name, String value) {
+      checkName(name);
       return addLenient(name, value);
     }
 
@@ -345,7 +360,8 @@ public Builder removeAll(String name) {
      * found, the existing values are replaced.
      */
     public Builder set(String name, String value) {
-      checkNameAndValue(name, value);
+      checkName(name);
+      checkValue(value, name);
       removeAll(name);
       addLenient(name, value);
       return this;