diff --git a/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CaseInsensitiveDictionary.java b/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CaseInsensitiveDictionary.java
new file mode 100644
index 0000000000..c476ad7246
--- /dev/null
+++ b/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CaseInsensitiveDictionary.java
@@ -0,0 +1,78 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
+ */
+package org.hibernate.internal.util.collections;
+
+import java.util.Collections;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.BiConsumer;
+
+import org.hibernate.Internal;
+
+/**
+ * Wraps a ConcurrentHashMap having all keys as Strings
+ * and ensures all keys are lowercased.
+ * It does assume keys and arguments are never null, preferring to throw a NPE
+ * over adding unnecessary checks.
+ * The public exposed methods are similar to the ones on Map, but
+ * not all Map methods are exposed - only a selection we actually need; this
+ * implies it doesn't implement Map; nothing stops us to make it implement Map
+ * but at time of writing it seems unnecessary for our purposes.
+ * @param <V> the type for the stored values.
+ */
+@Internal
+public final class CaseInsensitiveDictionary<V> {
+
+	private final Map<String, V> map = new ConcurrentHashMap<>();
+
+	public V get(final String key) {
+		return map.get( trueKey( key ) );
+	}
+
+	/**
+	 * Contrary to traditional Map, we make the return unmodifiable.
+	 * @return the map's keySet
+	 */
+	public Set<String> unmodifiableKeySet() {
+		return Collections.unmodifiableSet( map.keySet() );
+	}
+
+	/**
+	 * Contrary to traditional Map, we make the return unmodifiable.
+	 * @return the map's entrySet
+	 */
+	public Set<Map.Entry<String, V>> unmodifiableEntrySet() {
+		return Collections.unmodifiableSet( map.entrySet() );
+	}
+
+	public V put(final String key, V value) {
+		return map.put( trueKey( key ), value );
+	}
+
+	public V remove(final String key) {
+		return map.remove( trueKey( key ) );
+	}
+
+	public boolean containsKey(final String key) {
+		return map.containsKey( trueKey( key ) );
+	}
+
+	private static String trueKey(final String key) {
+		return key.toLowerCase( Locale.ROOT );
+	}
+
+	public void clear() {
+		map.clear();
+	}
+
+	public void forEach(final BiConsumer<? super String, ? super V> action) {
+		map.forEach( action );
+	}
+
+}
diff --git a/hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionRegistry.java b/hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionRegistry.java
index b861bb427a..0341e3edbc 100644
--- a/hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionRegistry.java
+++ b/hibernate-core/src/main/java/org/hibernate/query/sqm/function/SqmFunctionRegistry.java
@@ -6,11 +6,12 @@
  */
 package org.hibernate.query.sqm.function;
 
-import java.util.AbstractMap;
 import java.util.Map;
+import java.util.Set;
 import java.util.TreeMap;
 import java.util.stream.Stream;
 
+import org.hibernate.internal.util.collections.CaseInsensitiveDictionary;
 import org.hibernate.query.sqm.produce.function.FunctionParameterType;
 import org.hibernate.query.sqm.produce.function.NamedFunctionDescriptorBuilder;
 import org.hibernate.query.sqm.produce.function.PatternFunctionDescriptorBuilder;
@@ -35,27 +36,31 @@ import static org.hibernate.query.sqm.produce.function.StandardFunctionReturnTyp
 public class SqmFunctionRegistry {
 	private static final Logger log = Logger.getLogger( SqmFunctionRegistry.class );
 
-	private final Map<String, SqmFunctionDescriptor> functionMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
-	private final Map<String,String> alternateKeyMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
+	private final CaseInsensitiveDictionary<SqmFunctionDescriptor> functionMap = new CaseInsensitiveDictionary<>();
+	private final CaseInsensitiveDictionary<String> alternateKeyMap = new CaseInsensitiveDictionary<>();
 
 	public SqmFunctionRegistry() {
 		log.trace( "SqmFunctionRegistry created" );
 	}
 
-	public Map<String, SqmFunctionDescriptor> getFunctions() {
-		return functionMap;
+	public Set<String> getValidFunctionKeys() {
+		return functionMap.unmodifiableKeySet();
 	}
 
+	/**
+	 * Useful for diagnostics - not efficient: do not use in production code.
+	 *
+	 * @return
+	 */
 	public Stream<Map.Entry<String, SqmFunctionDescriptor>> getFunctionsByName() {
-		return Stream.concat(
-				functionMap.entrySet().stream(),
-				alternateKeyMap.entrySet().stream().map(
-						entry -> new AbstractMap.SimpleEntry<>(
-								entry.getKey(),
-								functionMap.get( entry.getValue() )
-						)
-				)
-		);
+		final Map<String, SqmFunctionDescriptor> sortedFunctionMap = new TreeMap<>( CASE_INSENSITIVE_ORDER );
+		for ( Map.Entry<String, SqmFunctionDescriptor> e : functionMap.unmodifiableEntrySet() ) {
+			sortedFunctionMap.put( e.getKey(), e.getValue() );
+		}
+		for ( Map.Entry<String, String> e : alternateKeyMap.unmodifiableEntrySet() ) {
+			sortedFunctionMap.put( e.getKey(), functionMap.get( e.getValue() ) );
+		}
+		return sortedFunctionMap.entrySet().stream();
 	}
 
 	/**
diff --git a/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/SpatialSessionFactoryAware.java b/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/SpatialSessionFactoryAware.java
index e52b48a691..11e583e7c5 100644
--- a/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/SpatialSessionFactoryAware.java
+++ b/hibernate-spatial/src/test/java/org/hibernate/spatial/testing/SpatialSessionFactoryAware.java
@@ -35,8 +35,7 @@ public abstract class SpatialSessionFactoryAware extends SpatialTestDataProvider
 			this.supportedFunctions = scope.getSessionFactory()
 					.getQueryEngine()
 					.getSqmFunctionRegistry()
-					.getFunctions()
-					.keySet();
+					.getValidFunctionKeys();
 			if ( DialectContext.getDialect() instanceof H2Dialect ) {
 				initH2GISExtensionsForInMemDb();
 			}