diff --git a/extensions/resteasy-classic/rest-client-config/runtime/src/main/java/io/quarkus/restclient/config/RestClientsConfig.java b/extensions/resteasy-classic/rest-client-config/runtime/src/main/java/io/quarkus/restclient/config/RestClientsConfig.java
index 2019f5ab507a47..bf83707b5eacc2 100644
--- a/extensions/resteasy-classic/rest-client-config/runtime/src/main/java/io/quarkus/restclient/config/RestClientsConfig.java
+++ b/extensions/resteasy-classic/rest-client-config/runtime/src/main/java/io/quarkus/restclient/config/RestClientsConfig.java
@@ -15,9 +15,11 @@
 import io.quarkus.runtime.annotations.ConfigPhase;
 import io.quarkus.runtime.annotations.ConfigRoot;
 import io.quarkus.runtime.configuration.MemorySize;
+import io.quarkus.runtime.configuration.TrimmedStringConverter;
 import io.smallrye.config.ConfigMapping;
 import io.smallrye.config.ConfigValue;
 import io.smallrye.config.SmallRyeConfig;
+import io.smallrye.config.WithConverter;
 import io.smallrye.config.WithDefault;
 import io.smallrye.config.WithDefaults;
 import io.smallrye.config.WithKeys;
@@ -58,6 +60,7 @@ public interface RestClientsConfig {
      * <p>
      * Can be overwritten by client-specific settings.
      */
+    @WithConverter(TrimmedStringConverter.class)
     Optional<String> proxyAddress();
 
     /**