diff --git a/README.md b/README.md
index adea97d..4e401f3 100644
--- a/README.md
+++ b/README.md
@@ -712,6 +712,12 @@ more results? (y/n): n
 
 # Change Log
 
+## [1.22](https://github.com/vincentrussell/sql-to-mongo-db-query-converter/tree/sql-to-mongo-db-query-converter-1.21) (2024-04-09)
+
+**Bugs:**
+
+- Custom functions weren't being parsed correctly
+
 
 ## [1.21](https://github.com/vincentrussell/sql-to-mongo-db-query-converter/tree/sql-to-mongo-db-query-converter-1.21) (2022-03-21)
 
diff --git a/src/main/java/com/github/vincentrussell/query/mongodb/sql/converter/processor/WhereClauseProcessor.java b/src/main/java/com/github/vincentrussell/query/mongodb/sql/converter/processor/WhereClauseProcessor.java
index 0fc6817..34115fd 100644
--- a/src/main/java/com/github/vincentrussell/query/mongodb/sql/converter/processor/WhereClauseProcessor.java
+++ b/src/main/java/com/github/vincentrussell/query/mongodb/sql/converter/processor/WhereClauseProcessor.java
@@ -95,8 +95,9 @@ private void parseComparativeExpr(final Document query, final Expression leftExp
             Document doc = new Document();
             Object leftParse = parseExpression(new Document(), leftExpression, rightExpression);
             Object rightParse = parseExpression(new Document(), rightExpression, leftExpression);
-            doc.put(operator, Arrays.asList(leftParse, (SqlUtils.isColumn(rightExpression)
-                    && !rightExpression.toString().startsWith("$") ? "$" + rightParse : rightParse)));
+            doc.put(operator, Arrays.asList(leftParse, ((SqlUtils.isColumn(rightExpression)
+                        && !rightExpression.toString().startsWith("$")
+                        && !Document.class.isInstance(leftParse)) ? "$" + rightParse : rightParse)));
             if (requiresMultistepAggregation) {
                 query.put("$expr", doc);
             } else {
@@ -117,10 +118,11 @@ private void parseComparativeExpr(final Document query, final Expression leftExp
             }
         } else if (Function.class.isInstance(rightExpression)) {
             Document doc = new Document();
-            Object leftParse = parseExpression(new Document(), rightExpression, leftExpression);
-            Object rightParse = parseExpression(new Document(), leftExpression, rightExpression);
-            doc.put(operator, Arrays.asList(leftParse, (SqlUtils.isColumn(leftExpression)
-                    && !leftExpression.toString().startsWith("$") ? "$" + rightParse : rightParse)));
+            Object leftParse = parseExpression(new Document(), leftExpression, rightExpression);
+            Object rightParse = parseExpression(new Document(), rightExpression, leftExpression);
+            doc.put(operator, Arrays.asList(leftParse, ((SqlUtils.isColumn(leftExpression)
+                    && !leftExpression.toString().startsWith("$")
+                    && !Document.class.isInstance(rightParse)) ? "$" + rightParse : rightParse)));
             if (requiresMultistepAggregation) {
                 query.put("$expr", doc);
             } else {
diff --git a/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterJoinTest.java b/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterJoinTest.java
index db4a1a8..7e5565e 100644
--- a/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterJoinTest.java
+++ b/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterJoinTest.java
@@ -895,81 +895,81 @@ public void writeJoinWithAllCount() throws ParseException, IOException {
         QueryConverter queryConverter = new QueryConverter.Builder().sqlString("select count(*) from Table1 as t join Table2 as e on e._id = OID(t.Table1.eventId) where 1 = 1 AND t.Table1.eventId='111111' AND e.Table2.tid='2222222'").build();
         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
         queryConverter.write(byteArrayOutputStream);
-        assertEquals("db.Table1.aggregate([{\n" + 
-        		"  \"$match\": {\n" + 
-        		"    \"$and\": [\n" + 
-        		"      {\n" + 
-        		"        \"$expr\": {\n" + 
-        		"          \"$eq\": [\n" + 
-        		"            1,\n" + 
-        		"            1\n" + 
-        		"          ]\n" + 
-        		"        }\n" + 
-        		"      },\n" + 
-        		"      {\n" + 
-        		"        \"Table1.eventId\": \"111111\"\n" + 
-        		"      }\n" + 
-        		"    ]\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$lookup\": {\n" + 
-        		"    \"from\": \"Table2\",\n" + 
-        		"    \"let\": {\n" + 
-        		"      \"table1_eventid\": \"$Table1.eventId\"\n" + 
-        		"    },\n" + 
-        		"    \"pipeline\": [\n" + 
-        		"      {\n" + 
-        		"        \"$match\": {\n" + 
-        		"          \"$and\": [\n" + 
-        		"            {\n" + 
-        		"              \"$expr\": {\n" + 
-        		"                \"$eq\": [\n" + 
-        		"                  {\n" + 
-        		"                    \"$toObjectId\": \"$$table1_eventid\"\n" + 
-        		"                  },\n" + 
-        		"                  \"$_id\"\n" + 
-        		"                ]\n" + 
-        		"              }\n" + 
-        		"            },\n" + 
-        		"            {\n" + 
-        		"              \"$and\": [\n" + 
-        		"                {\n" + 
-        		"                  \"$expr\": {\n" + 
-        		"                    \"$eq\": [\n" + 
-        		"                      1,\n" + 
-        		"                      1\n" + 
-        		"                    ]\n" + 
-        		"                  }\n" + 
-        		"                },\n" + 
-        		"                {\n" + 
-        		"                  \"Table2.tid\": \"2222222\"\n" + 
-        		"                }\n" + 
-        		"              ]\n" + 
-        		"            }\n" + 
-        		"          ]\n" + 
-        		"        }\n" + 
-        		"      }\n" + 
-        		"    ],\n" + 
-        		"    \"as\": \"e\"\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$unwind\": {\n" + 
-        		"    \"path\": \"$e\",\n" + 
-        		"    \"preserveNullAndEmptyArrays\": false\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$group\": {\n" + 
-        		"    \"_id\": {},\n" + 
-        		"    \"count\": {\n" + 
-        		"      \"$sum\": 1\n" + 
-        		"    }\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$project\": {\n" + 
-        		"    \"count\": 1,\n" + 
-        		"    \"_id\": 0\n" + 
-        		"  }\n" + 
-        		"}])",byteArrayOutputStream.toString("UTF-8"));
+        assertEquals("db.Table1.aggregate([{\n"
+                      + "  \"$match\": {\n"
+                      + "    \"$and\": [\n"
+                      + "      {\n"
+                      + "        \"$expr\": {\n"
+                      + "          \"$eq\": [\n"
+                      + "            1,\n"
+                      + "            1\n"
+                      + "          ]\n"
+                      + "        }\n"
+                      + "      },\n"
+                      + "      {\n"
+                      + "        \"Table1.eventId\": \"111111\"\n"
+                      + "      }\n"
+                      + "    ]\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$lookup\": {\n"
+                      + "    \"from\": \"Table2\",\n"
+                      + "    \"let\": {\n"
+                      + "      \"table1_eventid\": \"$Table1.eventId\"\n"
+                      + "    },\n"
+                      + "    \"pipeline\": [\n"
+                      + "      {\n"
+                      + "        \"$match\": {\n"
+                      + "          \"$and\": [\n"
+                      + "            {\n"
+                      + "              \"$expr\": {\n"
+                      + "                \"$eq\": [\n"
+                      + "                  \"$_id\",\n"
+                      + "                  {\n"
+                      + "                    \"$toObjectId\": \"$$table1_eventid\"\n"
+                      + "                  }\n"
+                      + "                ]\n"
+                      + "              }\n"
+                      + "            },\n"
+                      + "            {\n"
+                      + "              \"$and\": [\n"
+                      + "                {\n"
+                      + "                  \"$expr\": {\n"
+                      + "                    \"$eq\": [\n"
+                      + "                      1,\n"
+                      + "                      1\n"
+                      + "                    ]\n"
+                      + "                  }\n"
+                      + "                },\n"
+                      + "                {\n"
+                      + "                  \"Table2.tid\": \"2222222\"\n"
+                      + "                }\n"
+                      + "              ]\n"
+                      + "            }\n"
+                      + "          ]\n"
+                      + "        }\n"
+                      + "      }\n"
+                      + "    ],\n"
+                      + "    \"as\": \"e\"\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$unwind\": {\n"
+                      + "    \"path\": \"$e\",\n"
+                      + "    \"preserveNullAndEmptyArrays\": false\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$group\": {\n"
+                      + "    \"_id\": {},\n"
+                      + "    \"count\": {\n"
+                      + "      \"$sum\": 1\n"
+                      + "    }\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$project\": {\n"
+                      + "    \"count\": 1,\n"
+                      + "    \"_id\": 0\n"
+                      + "  }\n"
+                      + "}])",byteArrayOutputStream.toString("UTF-8"));
     }
     
     @Test
@@ -977,81 +977,81 @@ public void writeJoinWithAllCountNestedDif() throws ParseException, IOException
         QueryConverter queryConverter = new QueryConverter.Builder().sqlString("select count(*) from Table1 as t join Table2 as e on e._id = OID(t.root1.eventId) where 1 = 1 AND t.root1.eventId='111111' AND e.root2.tid='2222222'").build();
         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
         queryConverter.write(byteArrayOutputStream);
-        assertEquals("db.Table1.aggregate([{\n" + 
-        		"  \"$match\": {\n" + 
-        		"    \"$and\": [\n" + 
-        		"      {\n" + 
-        		"        \"$expr\": {\n" + 
-        		"          \"$eq\": [\n" + 
-        		"            1,\n" + 
-        		"            1\n" + 
-        		"          ]\n" + 
-        		"        }\n" + 
-        		"      },\n" + 
-        		"      {\n" + 
-        		"        \"root1.eventId\": \"111111\"\n" + 
-        		"      }\n" + 
-        		"    ]\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$lookup\": {\n" + 
-        		"    \"from\": \"Table2\",\n" + 
-        		"    \"let\": {\n" + 
-        		"      \"root1_eventid\": \"$root1.eventId\"\n" + 
-        		"    },\n" + 
-        		"    \"pipeline\": [\n" + 
-        		"      {\n" + 
-        		"        \"$match\": {\n" + 
-        		"          \"$and\": [\n" + 
-        		"            {\n" + 
-        		"              \"$expr\": {\n" + 
-        		"                \"$eq\": [\n" + 
-        		"                  {\n" + 
-        		"                    \"$toObjectId\": \"$$root1_eventid\"\n" + 
-        		"                  },\n" + 
-        		"                  \"$_id\"\n" + 
-        		"                ]\n" + 
-        		"              }\n" + 
-        		"            },\n" + 
-        		"            {\n" + 
-        		"              \"$and\": [\n" + 
-        		"                {\n" + 
-        		"                  \"$expr\": {\n" + 
-        		"                    \"$eq\": [\n" + 
-        		"                      1,\n" + 
-        		"                      1\n" + 
-        		"                    ]\n" + 
-        		"                  }\n" + 
-        		"                },\n" + 
-        		"                {\n" + 
-        		"                  \"root2.tid\": \"2222222\"\n" + 
-        		"                }\n" + 
-        		"              ]\n" + 
-        		"            }\n" + 
-        		"          ]\n" + 
-        		"        }\n" + 
-        		"      }\n" + 
-        		"    ],\n" + 
-        		"    \"as\": \"e\"\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$unwind\": {\n" + 
-        		"    \"path\": \"$e\",\n" + 
-        		"    \"preserveNullAndEmptyArrays\": false\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$group\": {\n" + 
-        		"    \"_id\": {},\n" + 
-        		"    \"count\": {\n" + 
-        		"      \"$sum\": 1\n" + 
-        		"    }\n" + 
-        		"  }\n" + 
-        		"},{\n" + 
-        		"  \"$project\": {\n" + 
-        		"    \"count\": 1,\n" + 
-        		"    \"_id\": 0\n" + 
-        		"  }\n" + 
-        		"}])",byteArrayOutputStream.toString("UTF-8"));
+        assertEquals("db.Table1.aggregate([{\n"
+                      + "  \"$match\": {\n"
+                      + "    \"$and\": [\n"
+                      + "      {\n"
+                      + "        \"$expr\": {\n"
+                      + "          \"$eq\": [\n"
+                      + "            1,\n"
+                      + "            1\n"
+                      + "          ]\n"
+                      + "        }\n"
+                      + "      },\n"
+                      + "      {\n"
+                      + "        \"root1.eventId\": \"111111\"\n"
+                      + "      }\n"
+                      + "    ]\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$lookup\": {\n"
+                      + "    \"from\": \"Table2\",\n"
+                      + "    \"let\": {\n"
+                      + "      \"root1_eventid\": \"$root1.eventId\"\n"
+                      + "    },\n"
+                      + "    \"pipeline\": [\n"
+                      + "      {\n"
+                      + "        \"$match\": {\n"
+                      + "          \"$and\": [\n"
+                      + "            {\n"
+                      + "              \"$expr\": {\n"
+                      + "                \"$eq\": [\n"
+                      + "                  \"$_id\",\n"
+                      + "                  {\n"
+                      + "                    \"$toObjectId\": \"$$root1_eventid\"\n"
+                      + "                  }\n"
+                      + "                ]\n"
+                      + "              }\n"
+                      + "            },\n"
+                      + "            {\n"
+                      + "              \"$and\": [\n"
+                      + "                {\n"
+                      + "                  \"$expr\": {\n"
+                      + "                    \"$eq\": [\n"
+                      + "                      1,\n"
+                      + "                      1\n"
+                      + "                    ]\n"
+                      + "                  }\n"
+                      + "                },\n"
+                      + "                {\n"
+                      + "                  \"root2.tid\": \"2222222\"\n"
+                      + "                }\n"
+                      + "              ]\n"
+                      + "            }\n"
+                      + "          ]\n"
+                      + "        }\n"
+                      + "      }\n"
+                      + "    ],\n"
+                      + "    \"as\": \"e\"\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$unwind\": {\n"
+                      + "    \"path\": \"$e\",\n"
+                      + "    \"preserveNullAndEmptyArrays\": false\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$group\": {\n"
+                      + "    \"_id\": {},\n"
+                      + "    \"count\": {\n"
+                      + "      \"$sum\": 1\n"
+                      + "    }\n"
+                      + "  }\n"
+                      + "},{\n"
+                      + "  \"$project\": {\n"
+                      + "    \"count\": 1,\n"
+                      + "    \"_id\": 0\n"
+                      + "  }\n"
+                      + "}])",byteArrayOutputStream.toString("UTF-8"));
     }
 
 
diff --git a/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterTest.java b/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterTest.java
index 14a5236..4bf9819 100644
--- a/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterTest.java
+++ b/src/test/java/com/github/vincentrussell/query/mongodb/sql/converter/QueryConverterTest.java
@@ -96,6 +96,27 @@ public void betweenWithDates() throws ParseException, java.text.ParseException {
         assertEquals(documentValuesArray("$and", document("date", document("$gte", toDate("yyyy-MM-dd", "2012-12-01"))),
                 document("date", document("$lte", toDate("yyyy-MM-dd", "2012-12-02")))), mongoDBQueryHolder.getQuery());
     }
+    
+        @Test
+        public void functionsStayOnSameSideOfOperandLeftSide() throws ParseException {
+            QueryConverter queryConverter = new QueryConverter.Builder().sqlString("select * from table where beginningOfMonth(-1) < eventTime").build();
+            MongoDBQueryHolder mongoDBQueryHolder = queryConverter.getMongoQuery();
+            assertEquals(document("$lt", objsToList(document("$beginningOfMonth", Long.parseLong("-1")), "eventTime")), mongoDBQueryHolder.getQuery());
+        }
+    
+    @Test
+    public void functionsStayOnSameSideOfOperandRightSide() throws ParseException {
+        QueryConverter queryConverter = new QueryConverter.Builder().sqlString("select * from table where eventTime > beginningOfMonth(-1)").build();
+        MongoDBQueryHolder mongoDBQueryHolder = queryConverter.getMongoQuery();
+        assertEquals(document("$gt", objsToList("eventTime", document("$beginningOfMonth", Long.parseLong("-1")))), mongoDBQueryHolder.getQuery());
+    }
+    
+    @Test
+    public void functionsOnBothSide() throws ParseException {
+        QueryConverter queryConverter = new QueryConverter.Builder().sqlString("select * from table where beginningOfMonth(-1) > beginningOfMonth(-1)").build();
+        MongoDBQueryHolder mongoDBQueryHolder = queryConverter.getMongoQuery();
+        assertEquals(document("$gt", objsToList(document("$beginningOfMonth", Long.parseLong("-1")), document("$beginningOfMonth", Long.parseLong("-1")))), mongoDBQueryHolder.getQuery());
+    }
 
     @Test
     public void selectFieldSurroundedInQuotesInFunctions() throws ParseException {