diff --git a/library/src/androidTest/java/com/bumptech/glide/load/model/LazyHeadersTest.java b/library/src/androidTest/java/com/bumptech/glide/load/model/LazyHeadersTest.java
index 98d3df0252..3b169456e2 100644
--- a/library/src/androidTest/java/com/bumptech/glide/load/model/LazyHeadersTest.java
+++ b/library/src/androidTest/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, emulateSdk = 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() {
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 2933d8bb1b..715ad85ff2 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
@@ -115,9 +115,9 @@ 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.