diff --git a/hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculator.java b/hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculator.java
index f28a48a5d23..126041ca69b 100644
--- a/hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculator.java
+++ b/hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculator.java
@@ -251,20 +251,14 @@ protected void calculate(CollectRep.MetricsData metricsData) {
                     }
                     final int fieldType = field.getType();
 
+                    // strict jexl aborts the whole rule on undefined variables,
+                    // so define every field even when its value is empty or unparseable
                     if (fieldType == CommonConstants.TYPE_NUMBER) {
-                        final Double doubleValue;
-                        if ((doubleValue = CommonUtil.parseStrDouble(valueStr)) != null) {
-                            fieldValueMap.put(field.getName(), doubleValue);
-                        }
+                        fieldValueMap.put(field.getName(), CommonUtil.parseStrDouble(valueStr));
                     } else if (fieldType == CommonConstants.TYPE_TIME) {
-                        final Integer integerValue;
-                        if ((integerValue = CommonUtil.parseStrInteger(valueStr)) != null) {
-                            fieldValueMap.put(field.getName(), integerValue);
-                        }
+                        fieldValueMap.put(field.getName(), CommonUtil.parseStrInteger(valueStr));
                     } else {
-                        if (StringUtils.isNotEmpty(valueStr)) {
-                            fieldValueMap.put(field.getName(), valueStr);
-                        }
+                        fieldValueMap.put(field.getName(), valueStr);
                     }
 
                     if (field.getLabel()) {
diff --git a/hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculatorMatchTest.java b/hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculatorMatchTest.java
index 6844bb1bcb5..44929a5d297 100644
--- a/hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculatorMatchTest.java
+++ b/hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/calculate/realtime/MetricsRealTimeAlertCalculatorMatchTest.java
@@ -27,11 +27,13 @@
 import org.apache.hertzbeat.common.constants.CommonConstants;
 import org.apache.hertzbeat.common.constants.MetricDataConstants;
 import org.apache.hertzbeat.common.entity.alerter.AlertDefine;
+import org.apache.hertzbeat.common.entity.alerter.SingleAlert;
 import org.apache.hertzbeat.common.entity.message.CollectRep;
 import org.apache.hertzbeat.common.queue.CommonDataQueue;
 import org.apache.hertzbeat.common.queue.impl.InMemoryCommonDataQueue;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -43,6 +45,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -254,4 +257,89 @@ void testCalculateWithNormalApp() throws InterruptedException {
         verify(alarmCommonReduce, times(1)).reduceAndSendAlarm(any());
     }
 
+    @Test
+    void testEmptyStringFieldStillTriggersAlert() throws InterruptedException {
+        CollectRep.MetricsData.Builder builder = CollectRep.MetricsData.newBuilder();
+        builder.setId(518679137103104L)
+                .setApp("fullsite")
+                .setMetrics("summary")
+                .setPriority(1)
+                .setCode(CollectRep.Code.SUCCESS);
+
+        CollectRep.Field url = CollectRep.Field.newBuilder().setName("url").setType(CommonConstants.TYPE_STRING).setLabel(true).build();
+        CollectRep.Field statusCode = CollectRep.Field.newBuilder().setName("statusCode").setType(CommonConstants.TYPE_STRING).build();
+        CollectRep.Field errorMsg = CollectRep.Field.newBuilder().setName("errorMsg").setType(CommonConstants.TYPE_STRING).build();
+
+        Map<String, String> meta = new HashMap<>();
+        meta.put(MetricDataConstants.INSTANCE_NAME, "site");
+        meta.put(MetricDataConstants.INSTANCE, "127.0.0.1");
+
+        builder.addMetadataAll(meta);
+        builder.addAllFields(Lists.newArrayList(url, statusCode, errorMsg));
+        builder.addValueRow(CollectRep.ValueRow.newBuilder()
+                .addColumn("https://example.com/broken").addColumn("404").addColumn("").build());
+
+        CollectRep.MetricsData metricsData = builder.build();
+
+        AlertDefine matchDefine = new AlertDefine();
+        matchDefine.setId(1L);
+        matchDefine.setName("sitemap-status");
+        matchDefine.setExpr("equals(__app__,\"fullsite\") && !matches(statusCode,\"^2[0-9]+\") && !contains(errorMsg,\"timed out\")");
+        matchDefine.setTemplate("site down: ${url}");
+        matchDefine.setTimes(1);
+
+        when(alertDefineService.getMetricsRealTimeAlertDefines()).thenReturn(Collections.singletonList(matchDefine));
+        when(dataQueue.pollMetricsDataToAlerter()).thenReturn(metricsData).thenThrow(new InterruptedException());
+
+        metricsRealTimeAlertCalculator.startCalculate();
+
+        Thread.sleep(3000);
+
+        ArgumentCaptor<SingleAlert> alertCaptor = ArgumentCaptor.forClass(SingleAlert.class);
+        verify(alarmCommonReduce, times(1)).reduceAndSendAlarm(alertCaptor.capture());
+        assertEquals("site down: https://example.com/broken", alertCaptor.getValue().getContent());
+    }
+
+    @Test
+    void testUnparseableNumberFieldDoesNotAbortRule() throws InterruptedException {
+        CollectRep.MetricsData.Builder builder = CollectRep.MetricsData.newBuilder();
+        builder.setId(518679137103105L)
+                .setApp("fullsite")
+                .setMetrics("summary")
+                .setPriority(1)
+                .setCode(CollectRep.Code.SUCCESS);
+
+        CollectRep.Field url = CollectRep.Field.newBuilder().setName("url").setType(CommonConstants.TYPE_STRING).setLabel(true).build();
+        CollectRep.Field responseTime = CollectRep.Field.newBuilder().setName("responseTime").setType(CommonConstants.TYPE_NUMBER).build();
+
+        Map<String, String> meta = new HashMap<>();
+        meta.put(MetricDataConstants.INSTANCE_NAME, "site");
+        meta.put(MetricDataConstants.INSTANCE, "127.0.0.1");
+
+        builder.addMetadataAll(meta);
+        builder.addAllFields(Lists.newArrayList(url, responseTime));
+        builder.addValueRow(CollectRep.ValueRow.newBuilder()
+                .addColumn("https://example.com/a").addColumn("").build());
+
+        CollectRep.MetricsData metricsData = builder.build();
+
+        AlertDefine guardedDefine = new AlertDefine();
+        guardedDefine.setId(2L);
+        guardedDefine.setName("slow-site");
+        guardedDefine.setExpr("equals(__app__,\"fullsite\") && exists(responseTime) && responseTime > 100");
+        guardedDefine.setTemplate("slow: ${url}");
+        guardedDefine.setTimes(1);
+
+        when(alertDefineService.getMetricsRealTimeAlertDefines()).thenReturn(Collections.singletonList(guardedDefine));
+        when(dataQueue.pollMetricsDataToAlerter()).thenReturn(metricsData).thenThrow(new InterruptedException());
+
+        metricsRealTimeAlertCalculator.startCalculate();
+
+        Thread.sleep(3000);
+
+        // unparseable number is defined as null: exists() short-circuits to false, no alarm and no abort
+        verify(alarmCommonReduce, never()).reduceAndSendAlarm(any());
+        verify(alarmCacheManager, times(1)).removeFiring(any(), any());
+    }
+
 }