diff --git a/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoProject.java b/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoProject.java
index ee0721fe4a92..658d20a72ed4 100644
--- a/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoProject.java
+++ b/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoProject.java
@@ -78,7 +78,7 @@ public MongoProject(RelOptCluster cluster, RelTraitSet traitSet,
     for (Pair<RexNode, String> pair : getNamedProjects()) {
       final String name = pair.right;
       final String expr = pair.left.accept(translator);
-      items.add(expr.equals("'$" + name + "'")
+      items.add(expr.equals("\"$" + name + "\"")
           ? MongoRules.maybeQuote(name) + ": 1"
           : MongoRules.maybeQuote(name) + ": " + expr);
     }
diff --git a/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoRules.java b/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoRules.java
index fa10035746c2..c7e7d226c748 100644
--- a/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoRules.java
+++ b/mongodb/src/main/java/org/apache/calcite/adapter/mongodb/MongoRules.java
@@ -103,25 +103,13 @@ static List<String> mongoFieldNames(final RelDataType rowType) {
   }
 
   static String maybeQuote(String s) {
-    if (!needsQuote(s)) {
-      return s;
-    }
+    // MongoDB Extended JSON conforms to the JSON RFC. It is safe to use double quotes for
+    // everything.
     return quote(s);
   }
 
   static String quote(String s) {
-    return "'" + s + "'"; // TODO: handle embedded quotes
-  }
-
-  private static boolean needsQuote(String s) {
-    for (int i = 0, n = s.length(); i < n; i++) {
-      char c = s.charAt(i);
-      if (!Character.isJavaIdentifierPart(c)
-          || c == '$') {
-        return true;
-      }
-    }
-    return false;
+    return "\"" + s.replace("\"", "\\\"") + "\"";
   }
 
   /** Translator from {@link RexNode} to strings in MongoDB's expression
@@ -178,7 +166,7 @@ protected RexToMongoTranslator(JavaTypeFactory typeFactory,
     @Override public String visitCall(RexCall call) {
       String name = isItem(call);
       if (name != null) {
-        return "'$" + name + "'";
+        return "\"$" + name + "\"";
       }
       final List<String> strings = visitList(call.operands);
       if (call.getKind() == SqlKind.CAST) {
@@ -230,7 +218,7 @@ protected RexToMongoTranslator(JavaTypeFactory typeFactory,
     }
 
     private static String stripQuotes(String s) {
-      return s.startsWith("'") && s.endsWith("'")
+      return s.startsWith("\"") && s.endsWith("\"")
           ? s.substring(1, s.length() - 1)
           : s;
     }
diff --git a/mongodb/src/test/java/org/apache/calcite/adapter/mongodb/MongoAdapterTest.java b/mongodb/src/test/java/org/apache/calcite/adapter/mongodb/MongoAdapterTest.java
index 368340969398..949c2d24f919 100644
--- a/mongodb/src/test/java/org/apache/calcite/adapter/mongodb/MongoAdapterTest.java
+++ b/mongodb/src/test/java/org/apache/calcite/adapter/mongodb/MongoAdapterTest.java
@@ -119,6 +119,7 @@ public static void setUp() throws Exception {
     doc.put("ownerId", new BsonString("531e7789e4b0853ddb861313"));
     doc.put("arr", new BsonArray(Arrays.asList(new BsonString("a"), new BsonString("b"))));
     doc.put("binaryData", new BsonBinary("binaryData".getBytes(StandardCharsets.UTF_8)));
+    doc.put("1_minute_aggregation", new BsonInt32(10));
     datatypes.insertOne(doc);
 
     schema = new MongoSchema(database);
@@ -615,18 +616,22 @@ private CalciteAssert.AssertThat assertModel(URL url) {
                 "{$limit: 5}"));
   }
 
-  @Disabled("broken; [CALCITE-2115] is logged to fix it")
   @Test void testProject() {
     assertModel(MODEL)
         .query("select state, city, 0 as zero from zips order by state, city")
         .limit(2)
-        .returns("STATE=AK; CITY=AKHIOK; ZERO=0\n"
-            + "STATE=AK; CITY=AKIACHAK; ZERO=0\n")
+        .returns("STATE=AK; CITY=ANCHORAGE; ZERO=0\n"
+            + "STATE=AK; CITY=FAIRBANKS; ZERO=0\n")
         .queryContains(
             mongoChecker(
-                "{$project: {CITY: '$city', STATE: '$state'}}",
-                "{$sort: {STATE: 1, CITY: 1}}",
-                "{$project: {STATE: 1, CITY: 1, ZERO: {$literal: 0}}}"));
+                "{$project: {STATE: '$state', CITY: '$city', ZERO: {$literal: 0}}}",
+                "{$sort: {STATE: 1, CITY: 1}}"));
+
+    assertModel(MODEL)
+        .query("select cast(_MAP['1_minute_aggregation'] as INT) as \"1_minute_aggregation\" "
+            + "from \"mongo_raw\".\"datatypes\"")
+        .queryContains(
+            mongoChecker("{$project: {'1_minute_aggregation': 1}}"));
   }
 
   @Test void testFilter() {