diff --git a/implementation/src/main/java/io/smallrye/config/AbstractMappingConfigSourceInterceptor.java b/implementation/src/main/java/io/smallrye/config/AbstractMappingConfigSourceInterceptor.java
index 17568f402..923c059e7 100644
--- a/implementation/src/main/java/io/smallrye/config/AbstractMappingConfigSourceInterceptor.java
+++ b/implementation/src/main/java/io/smallrye/config/AbstractMappingConfigSourceInterceptor.java
@@ -1,9 +1,7 @@
 package io.smallrye.config;
 
-import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
-import java.util.Set;
 import java.util.function.Function;
 
 public abstract class AbstractMappingConfigSourceInterceptor implements ConfigSourceInterceptor {
@@ -26,17 +24,30 @@ public String apply(final String name) {
 
     @Override
     public Iterator<String> iterateNames(final ConfigSourceInterceptorContext context) {
-        final Set<String> names = new HashSet<>();
-        final Iterator<String> namesIterator = context.iterateNames();
-        while (namesIterator.hasNext()) {
-            final String name = namesIterator.next();
-            names.add(name);
-            final String mappedName = mapping.apply(name);
-            if (mappedName != null) {
-                names.add(mappedName);
+        return new Iterator<>() {
+            final Iterator<String> iterator = context.iterateNames();
+            String mappedName = null;
+
+            @Override
+            public boolean hasNext() {
+                return mappedName != null || iterator.hasNext();
+            }
+
+            @Override
+            public String next() {
+                if (mappedName != null) {
+                    String mappedName = this.mappedName;
+                    this.mappedName = null;
+                    return mappedName;
+                }
+                String name = iterator.next();
+                String mappedName = mapping.apply(name);
+                if (!name.equals(mappedName)) {
+                    this.mappedName = mappedName;
+                }
+                return name;
             }
-        }
-        return names.iterator();
+        };
     }
 
     protected Function<String, String> getMapping() {
diff --git a/implementation/src/main/java/io/smallrye/config/ProfileConfigSourceInterceptor.java b/implementation/src/main/java/io/smallrye/config/ProfileConfigSourceInterceptor.java
index e0dc37449..e91a0f6f4 100644
--- a/implementation/src/main/java/io/smallrye/config/ProfileConfigSourceInterceptor.java
+++ b/implementation/src/main/java/io/smallrye/config/ProfileConfigSourceInterceptor.java
@@ -7,10 +7,8 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Set;
 
 import jakarta.annotation.Priority;
 
@@ -66,12 +64,19 @@ public ConfigValue getProfileValue(final ConfigSourceInterceptorContext context,
 
     @Override
     public Iterator<String> iterateNames(final ConfigSourceInterceptorContext context) {
-        final Set<String> names = new HashSet<>();
-        final Iterator<String> namesIterator = context.iterateNames();
-        while (namesIterator.hasNext()) {
-            names.add(activeName(namesIterator.next(), profiles));
-        }
-        return names.iterator();
+        return new Iterator<>() {
+            final Iterator<String> iterator = context.iterateNames();
+
+            @Override
+            public boolean hasNext() {
+                return iterator.hasNext();
+            }
+
+            @Override
+            public String next() {
+                return activeName(iterator.next(), profiles);
+            }
+        };
     }
 
     public List<String> getProfiles() {
diff --git a/implementation/src/main/java/io/smallrye/config/SmallRyeConfigSources.java b/implementation/src/main/java/io/smallrye/config/SmallRyeConfigSources.java
index 17deef2a2..5e545239a 100644
--- a/implementation/src/main/java/io/smallrye/config/SmallRyeConfigSources.java
+++ b/implementation/src/main/java/io/smallrye/config/SmallRyeConfigSources.java
@@ -1,8 +1,9 @@
 package io.smallrye.config;
 
+import static java.util.Collections.emptyIterator;
+
 import java.io.Serializable;
 import java.util.ArrayList;
-import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -43,16 +44,36 @@ public ConfigValue getValue(final ConfigSourceInterceptorContext context, final
 
     @Override
     public Iterator<String> iterateNames(final ConfigSourceInterceptorContext context) {
-        final Set<String> names = new HashSet<>();
-        for (final ConfigValueConfigSource configSource : configSources) {
-            final Set<String> propertyNames = configSource.getPropertyNames();
-            if (propertyNames != null) {
-                names.addAll(propertyNames);
+        return new Iterator<>() {
+            final Iterator<ConfigValueConfigSource> configSourceIterator = configSources.iterator();
+            Iterator<String> propertiesIterator = context.iterateNames();
+
+            @Override
+            public boolean hasNext() {
+                if (propertiesIterator.hasNext()) {
+                    return true;
+                } else {
+                    propertiesIterator = nextConfigSource();
+                    if (propertiesIterator.hasNext()) {
+                        return true;
+                    } else if (configSourceIterator.hasNext()) {
+                        return hasNext();
+                    } else {
+                        return false;
+                    }
+                }
             }
-        }
-        Iterator<String> iter = context.iterateNames();
-        iter.forEachRemaining(names::add);
-        return names.iterator();
+
+            @Override
+            public String next() {
+                return propertiesIterator.next();
+            }
+
+            private Iterator<String> nextConfigSource() {
+                return configSourceIterator.hasNext() ? configSourceIterator.next().getPropertyNames().iterator()
+                        : emptyIterator();
+            }
+        };
     }
 
     boolean negative() {