diff --git a/gson/src/main/java/com/google/gson/Gson.java b/gson/src/main/java/com/google/gson/Gson.java
index a06f290747..5fb67d1c32 100644
--- a/gson/src/main/java/com/google/gson/Gson.java
+++ b/gson/src/main/java/com/google/gson/Gson.java
@@ -1195,7 +1195,7 @@ public <T> T fromJson(JsonElement json, TypeToken<T> typeOfT) throws JsonSyntaxE
 
   private static void assertFullConsumption(Object obj, JsonReader reader) {
     try {
-      if (obj != null && reader.peek() != JsonToken.END_DOCUMENT) {
+      if (reader.peek() != JsonToken.END_DOCUMENT) {
         throw new JsonSyntaxException("JSON document was not fully consumed.");
       }
     } catch (MalformedJsonException e) {
diff --git a/gson/src/main/java/com/google/gson/JsonParser.java b/gson/src/main/java/com/google/gson/JsonParser.java
index d56da87a48..b2fafdd8d6 100644
--- a/gson/src/main/java/com/google/gson/JsonParser.java
+++ b/gson/src/main/java/com/google/gson/JsonParser.java
@@ -108,7 +108,7 @@ public static JsonElement parseReader(Reader reader) throws JsonIOException, Jso
     try {
       JsonReader jsonReader = new JsonReader(reader);
       JsonElement element = parseReader(jsonReader);
-      if (!element.isJsonNull() && jsonReader.peek() != JsonToken.END_DOCUMENT) {
+      if (jsonReader.peek() != JsonToken.END_DOCUMENT) {
         throw new JsonSyntaxException("Did not consume the entire document.");
       }
       return element;
diff --git a/gson/src/main/java/com/google/gson/internal/bind/JsonTreeReader.java b/gson/src/main/java/com/google/gson/internal/bind/JsonTreeReader.java
index 759310ea20..9f6c0b4d05 100644
--- a/gson/src/main/java/com/google/gson/internal/bind/JsonTreeReader.java
+++ b/gson/src/main/java/com/google/gson/internal/bind/JsonTreeReader.java
@@ -258,7 +258,29 @@ public long nextLong() throws IOException {
       throw new IllegalStateException(
           "Expected " + JsonToken.NUMBER + " but was " + token + locationString());
     }
-    long result = ((JsonPrimitive) peekStack()).getAsLong();
+    Object o = peekStack();
+    long result;
+    if (o instanceof JsonPrimitive) {
+      JsonPrimitive primitive = (JsonPrimitive) o;
+      if (primitive.isNumber()) {
+        Number number = primitive.getAsNumber();
+        if (number instanceof Long || number instanceof Integer) {
+          result = number.longValue();
+        } else {
+          // For other number types (e.g., Double, BigDecimal), check for loss of precision
+          double doubleValue = number.doubleValue();
+          result = (long) doubleValue;
+          if (result != doubleValue) {
+            throw new NumberFormatException(
+                "Expected a long but was " + number + locationString());
+          }
+        }
+      } else {
+        result = Long.parseLong(primitive.getAsString());
+      }
+    } else {
+      throw new IllegalStateException("Unexpected token: " + o);
+    }
     popStack();
     if (stackSize > 0) {
       pathIndices[stackSize - 1]++;
@@ -273,7 +295,29 @@ public int nextInt() throws IOException {
       throw new IllegalStateException(
           "Expected " + JsonToken.NUMBER + " but was " + token + locationString());
     }
-    int result = ((JsonPrimitive) peekStack()).getAsInt();
+    Object o = peekStack();
+    int result;
+    if (o instanceof JsonPrimitive) {
+      JsonPrimitive primitive = (JsonPrimitive) o;
+      if (primitive.isNumber()) {
+        Number number = primitive.getAsNumber();
+        if (number instanceof Integer) {
+          result = number.intValue();
+        } else {
+          // For other number types (e.g., Long, Double, BigDecimal), check for loss of precision
+          double doubleValue = number.doubleValue();
+          result = (int) doubleValue;
+          if (result != doubleValue) {
+            throw new NumberFormatException(
+                "Expected an int but was " + number + locationString());
+          }
+        }
+      } else {
+        result = Integer.parseInt(primitive.getAsString());
+      }
+    } else {
+      throw new IllegalStateException("Unexpected token: " + o);
+    }
     popStack();
     if (stackSize > 0) {
       pathIndices[stackSize - 1]++;
diff --git a/gson/src/test/java/com/google/gson/internal/bind/JsonTreeReaderTest.java b/gson/src/test/java/com/google/gson/internal/bind/JsonTreeReaderTest.java
index 42d4649683..f973eb8669 100644
--- a/gson/src/test/java/com/google/gson/internal/bind/JsonTreeReaderTest.java
+++ b/gson/src/test/java/com/google/gson/internal/bind/JsonTreeReaderTest.java
@@ -199,4 +199,27 @@ public void testOverrides() {
             "getNestingLimit()");
     MoreAsserts.assertOverridesMethods(JsonReader.class, JsonTreeReader.class, ignoredMethods);
   }
+
+  // Tests for issue #2817: Inconsistency JsonReader vs JsonTreeReader about double precision loss
+  @Test
+  public void testNextIntThrowsForDouble() throws IOException {
+    JsonObject json = new JsonObject();
+    json.addProperty("value", 42.123);
+    JsonTreeReader reader = new JsonTreeReader(json);
+    reader.beginObject();
+    reader.nextName();
+    NumberFormatException e = assertThrows(NumberFormatException.class, reader::nextInt);
+    assertThat(e).hasMessageThat().startsWith("Expected an int but was");
+  }
+
+  @Test
+  public void testNextLongThrowsForDouble() throws IOException {
+    JsonObject json = new JsonObject();
+    json.addProperty("value", 42.123);
+    JsonTreeReader reader = new JsonTreeReader(json);
+    reader.beginObject();
+    reader.nextName();
+    NumberFormatException e = assertThrows(NumberFormatException.class, reader::nextLong);
+    assertThat(e).hasMessageThat().startsWith("Expected a long but was");
+  }
 }