diff --git a/implementation/src/main/java/io/smallrye/config/ConfigValueConfigSource.java b/implementation/src/main/java/io/smallrye/config/ConfigValueConfigSource.java
index b0b1c7636..2bc2501d8 100644
--- a/implementation/src/main/java/io/smallrye/config/ConfigValueConfigSource.java
+++ b/implementation/src/main/java/io/smallrye/config/ConfigValueConfigSource.java
@@ -3,6 +3,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.Reader;
+import java.lang.invoke.MethodHandles;
 import java.util.AbstractCollection;
 import java.util.AbstractMap;
 import java.util.AbstractSet;
@@ -14,7 +15,9 @@
 import java.util.Set;
 
 import org.eclipse.microprofile.config.spi.ConfigSource;
+import org.jboss.logging.Logger;
 
+import io.smallrye.config._private.ConfigLogging;
 import io.smallrye.config._private.ConfigMessages;
 
 /**
@@ -340,6 +343,9 @@ final class ConfigValueProperties extends HashMap<String, ConfigValue> {
         private final String configSourceName;
         private final int configSourceOrdinal;
 
+        private static ConfigLogging log = Logger.getMessageLogger(MethodHandles.lookup(), ConfigLogging.class,
+                "io.smallrye.config");
+
         public ConfigValueProperties(final String configSourceName, final int configSourceOrdinal) {
             this.configSourceName = configSourceName;
             this.configSourceOrdinal = configSourceOrdinal;
@@ -401,7 +407,7 @@ private void load0(LineReader lr) throws IOException {
                 }
                 String key = loadConvert(lr.lineBuf, 0, keyLen, convtBuf);
                 String value = loadConvert(lr.lineBuf, valueStart, limit - valueStart, convtBuf);
-                put(key, ConfigValue.builder()
+                ConfigValue oldConfigValue = put(key, ConfigValue.builder()
                         .withName(key)
                         .withValue(value)
                         .withRawValue(value)
@@ -409,6 +415,10 @@ private void load0(LineReader lr) throws IOException {
                         .withConfigSourceOrdinal(configSourceOrdinal)
                         .withLineNumber(lr.lineNumber)
                         .build());
+                if (oldConfigValue != null) {
+                    ConfigLogging.log.duplicateValue(oldConfigValue.getName(), oldConfigValue.getConfigSourceName(),
+                            oldConfigValue.getValue());
+                }
             }
         }
 
diff --git a/implementation/src/main/java/io/smallrye/config/_private/ConfigLogging.java b/implementation/src/main/java/io/smallrye/config/_private/ConfigLogging.java
index aab962000..4feebaeb3 100644
--- a/implementation/src/main/java/io/smallrye/config/_private/ConfigLogging.java
+++ b/implementation/src/main/java/io/smallrye/config/_private/ConfigLogging.java
@@ -40,4 +40,9 @@ public interface ConfigLogging extends BasicLogger {
     @LogMessage(level = Logger.Level.DEBUG)
     @Message(id = 1006, value = "Loaded ConfigSource %s with ordinal %d")
     void loadedConfigSource(String name, int ordinal);
+
+    @LogMessage(level = Logger.Level.WARN)
+    @Message(id = 1007, value = "Duplicate value found for name : %s, config source name : %s, (old value : %s)")
+    void duplicateValue(String key, String sourceName, String oldValue);
+
 }
diff --git a/implementation/src/test/java/io/smallrye/config/ConfigValuePropertiesTest.java b/implementation/src/test/java/io/smallrye/config/ConfigValuePropertiesTest.java
index cc38375ba..a518eaee6 100644
--- a/implementation/src/test/java/io/smallrye/config/ConfigValuePropertiesTest.java
+++ b/implementation/src/test/java/io/smallrye/config/ConfigValuePropertiesTest.java
@@ -79,4 +79,17 @@ void wrapValue() throws Exception {
         assertEquals(2, map.get("key2").getLineNumber());
         assertEquals(6, map.get("key3").getLineNumber());
     }
+
+    @Test
+    void logDuplicateValue() throws Exception {
+        ConfigValueProperties map = new ConfigValueProperties("config", 1);
+        String config = "key=value\n" +
+                "key2=value\n" +
+                "key2=value2\n";
+        map.load(new StringReader(config));
+
+        // property expected with the last value found
+        assertEquals("value2", map.get("key2").getValue());
+    }
+
 }