diff --git a/moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java b/moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java
index 3f75ad5..c3cf28a 100644
--- a/moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java
+++ b/moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java
@@ -228,7 +228,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
       List<AdapterMethod> adapterMethods, Type type, Set<? extends Annotation> annotations) {
     for (int i = 0, size = adapterMethods.size(); i < size; i++) {
       AdapterMethod adapterMethod = adapterMethods.get(i);
-      if (Types.equals(adapterMethod.type, type) && adapterMethod.annotations.equals(annotations)) {
+      if (adapterMethod.type.equals(type) && adapterMethod.annotations.equals(annotations)) {
         return adapterMethod;
       }
     }
@@ -244,7 +244,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
 
     public AdapterMethod(Type type,
         Set<? extends Annotation> annotations, Object adapter, Method method, boolean nullable) {
-      this.type = type;
+      this.type = Types.canonicalize(type);
       this.annotations = annotations;
       this.adapter = adapter;
       this.method = method;
diff --git a/moshi/src/main/java/com/squareup/moshi/Moshi.java b/moshi/src/main/java/com/squareup/moshi/Moshi.java
index ccbdb18..9ed05c1 100644
--- a/moshi/src/main/java/com/squareup/moshi/Moshi.java
+++ b/moshi/src/main/java/com/squareup/moshi/Moshi.java
@@ -22,7 +22,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -63,6 +62,8 @@ public final class Moshi {
 
   @SuppressWarnings("unchecked") // Factories are required to return only matching JsonAdapters.
   public <T> JsonAdapter<T> adapter(Type type, Set<? extends Annotation> annotations) {
+    type = Types.canonicalize(type);
+
     // If there's an equivalent adapter in the cache, we're done!
     Object cacheKey = cacheKey(type, annotations);
     synchronized (adapterCache) {
@@ -111,6 +112,8 @@ public final class Moshi {
   @SuppressWarnings("unchecked") // Factories are required to return only matching JsonAdapters.
   public <T> JsonAdapter<T> nextAdapter(JsonAdapter.Factory skipPast, Type type,
       Set<? extends Annotation> annotations) {
+    type = Types.canonicalize(type);
+
     int skipPastIndex = factories.indexOf(skipPast);
     if (skipPastIndex == -1) {
       throw new IllegalArgumentException("Unable to skip past unknown factory " + skipPast);
diff --git a/moshi/src/main/java/com/squareup/moshi/Types.java b/moshi/src/main/java/com/squareup/moshi/Types.java
index 56feb8c..1235232 100644
--- a/moshi/src/main/java/com/squareup/moshi/Types.java
+++ b/moshi/src/main/java/com/squareup/moshi/Types.java
@@ -76,15 +76,18 @@ public final class Types {
       return c.isArray() ? new GenericArrayTypeImpl(canonicalize(c.getComponentType())) : c;
 
     } else if (type instanceof ParameterizedType) {
+      if (type instanceof ParameterizedTypeImpl) return type;
       ParameterizedType p = (ParameterizedType) type;
       return new ParameterizedTypeImpl(p.getOwnerType(),
           p.getRawType(), p.getActualTypeArguments());
 
     } else if (type instanceof GenericArrayType) {
+      if (type instanceof GenericArrayTypeImpl) return type;
       GenericArrayType g = (GenericArrayType) type;
       return new GenericArrayTypeImpl(g.getGenericComponentType());
 
     } else if (type instanceof WildcardType) {
+      if (type instanceof WildcardTypeImpl) return type;
       WildcardType w = (WildcardType) type;
       return new WildcardTypeImpl(w.getUpperBounds(), w.getLowerBounds());
 
@@ -172,7 +175,7 @@ public final class Types {
           && va.getName().equals(vb.getName());
 
     } else {
-      // This isn't a supported type. Could be a generic array type, wildcard type, etc.
+      // This isn't a supported type.
       return false;
     }
   }
diff --git a/moshi/src/test/java/com/squareup/moshi/AdapterMethodsTest.java b/moshi/src/test/java/com/squareup/moshi/AdapterMethodsTest.java
index 1271c27..3a3b2fc 100644
--- a/moshi/src/test/java/com/squareup/moshi/AdapterMethodsTest.java
+++ b/moshi/src/test/java/com/squareup/moshi/AdapterMethodsTest.java
@@ -369,19 +369,7 @@ public final class AdapterMethodsTest {
         .build();
 
     // This class doesn't implement equals() and hashCode() as it should.
-    ParameterizedType listOfStringType = new ParameterizedType() {
-      @Override public Type[] getActualTypeArguments() {
-        return new Type[] { String.class };
-      }
-
-      @Override public Type getRawType() {
-        return List.class;
-      }
-
-      @Override public Type getOwnerType() {
-        return null;
-      }
-    };
+    ParameterizedType listOfStringType = brokenParameterizedType(0, List.class, String.class);
 
     JsonAdapter<List<String>> jsonAdapter = moshi.adapter(listOfStringType);
     assertThat(jsonAdapter.toJson(Arrays.asList("a", "b", "c"))).isEqualTo("\"a|b|c\"");
@@ -403,6 +391,21 @@ public final class AdapterMethodsTest {
     }
   }
 
+  /**
+   * Even when the types we use to look up JSON adapters are not equal, if they're equivalent they
+   * should return the same JsonAdapter instance.
+   */
+  @Test public void parameterizedTypeCacheKey() throws Exception {
+    Moshi moshi = new Moshi.Builder().build();
+
+    Type a = brokenParameterizedType(0, List.class, String.class);
+    Type b = brokenParameterizedType(1, List.class, String.class);
+    Type c = brokenParameterizedType(2, List.class, String.class);
+
+    assertThat(moshi.adapter(b)).isSameAs(moshi.adapter(a));
+    assertThat(moshi.adapter(c)).isSameAs(moshi.adapter(a));
+  }
+
   static class Point {
     final int x;
     final int y;
@@ -424,4 +427,34 @@ public final class AdapterMethodsTest {
   interface Shape {
     String draw();
   }
+
+  /**
+   * Returns a new parameterized type that doesn't implement {@link Object#equals} or {@link
+   * Object#hashCode} by value. These implementation defects are consistent with the parameterized
+   * type that shipped in some older versions of Android.
+   */
+  ParameterizedType brokenParameterizedType(
+      final int hashCode, final Class<?> rawType, final Type... typeArguments) {
+    return new ParameterizedType() {
+      @Override public Type[] getActualTypeArguments() {
+        return typeArguments;
+      }
+
+      @Override public Type getRawType() {
+        return rawType;
+      }
+
+      @Override public Type getOwnerType() {
+        return null;
+      }
+
+      @Override public boolean equals(Object other) {
+        return other == this;
+      }
+
+      @Override public int hashCode() {
+        return hashCode;
+      }
+    };
+  }
 }