diff --git a/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java b/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java
index 915185fbde..1e4328b9c1 100644
--- a/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java
+++ b/library/src/main/java/com/bumptech/glide/load/model/LazyHeaders.java
@@ -117,9 +117,9 @@ public static final class Builder {
     }
 
     private boolean copyOnModify = true;
-    private boolean isEncodingDefault = true;
     private Map<String, List<LazyHeaderFactory>> headers = DEFAULT_HEADERS;
-    private boolean isUserAgentDefault = headers.containsKey(DEFAULT_USER_AGENT);
+    private boolean isEncodingDefault = true;
+    private boolean isUserAgentDefault = true;
 
     /**
      * Adds a value for the given header and returns this builder.
diff --git a/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java b/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java
index 8e0269c4e1..04e4151a4c 100644
--- a/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java
+++ b/library/src/test/java/com/bumptech/glide/load/model/LazyHeadersTest.java
@@ -8,6 +8,8 @@
 
 import com.bumptech.glide.load.model.LazyHeaders.Builder;
 
+import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
@@ -18,6 +20,22 @@
 @RunWith(RobolectricTestRunner.class)
 @Config(manifest = Config.NONE, sdk = 18)
 public class LazyHeadersTest {
+  private static final String DEFAULT_USER_AGENT = "default_user_agent";
+  private static final String DEFAULT_USER_AGENT_PROPERTY = "http.agent";
+  private String initialUserAgent;
+
+  @Before
+  public void setUp() {
+    initialUserAgent = System.getProperty(DEFAULT_USER_AGENT_PROPERTY);
+    System.setProperty(DEFAULT_USER_AGENT_PROPERTY, DEFAULT_USER_AGENT);
+  }
+
+  @After
+  public void tearDown() {
+    if (initialUserAgent != null) {
+      System.setProperty(DEFAULT_USER_AGENT_PROPERTY, initialUserAgent);
+    }
+  }
 
   @Test
   public void testIncludesEagerHeaders() {