diff --git a/src/AutoMapper/Configuration/Conventions.cs b/src/AutoMapper/Configuration/Conventions.cs
index 191861472f..a57cb01af1 100644
--- a/src/AutoMapper/Configuration/Conventions.cs
+++ b/src/AutoMapper/Configuration/Conventions.cs
@@ -8,9 +8,9 @@ public interface ISourceToDestinationNameMapper
 public sealed class MemberConfiguration
 {
     NameSplitMember _nameSplitMember;
-    public INamingConvention SourceNamingConvention { get; set; } = PascalCaseNamingConvention.Instance;
-    public INamingConvention DestinationNamingConvention { get; set; } = PascalCaseNamingConvention.Instance;
-    public List<ISourceToDestinationNameMapper> NameToMemberMappers { get; } = new();
+    public INamingConvention SourceNamingConvention { get; set; }
+    public INamingConvention DestinationNamingConvention { get; set; }
+    public List<ISourceToDestinationNameMapper> NameToMemberMappers { get; } = [];
     public bool IsMatch(ProfileMap options, TypeDetails sourceTypeDetails, Type destType, Type destMemberType, string nameToSearch, List<MemberInfo> resolvers, bool isReverseMap)
     {
         var matchingMemberInfo = GetSourceMember(sourceTypeDetails, destType, destMemberType, nameToSearch);
@@ -45,10 +45,6 @@ public void Seal()
     }
     public void Merge(MemberConfiguration other)
     {
-        if (other == null)
-        {
-            return;
-        }
         var initialCount = NameToMemberMappers.Count;
         for (int index = 0; index < other.NameToMemberMappers.Count; index++)
         {
@@ -64,6 +60,8 @@ public void Merge(MemberConfiguration other)
             }
             NameToMemberMappers.Add(otherMapper);
         }
+        SourceNamingConvention ??= other.SourceNamingConvention;
+        DestinationNamingConvention ??= other.DestinationNamingConvention;
     }
 }
 public sealed class PrePostfixName : ISourceToDestinationNameMapper
diff --git a/src/AutoMapper/ProfileMap.cs b/src/AutoMapper/ProfileMap.cs
index 5b0ae92417..3e05b50645 100644
--- a/src/AutoMapper/ProfileMap.cs
+++ b/src/AutoMapper/ProfileMap.cs
@@ -27,7 +27,15 @@ public ProfileMap(IProfileConfiguration profile, IGlobalConfigurationExpression
         ValueTransformers = profile.ValueTransformers.Concat(configuration?.ValueTransformers).ToArray();
         var profileInternal = (IProfileExpressionInternal)profile;
         MemberConfiguration = profileInternal.MemberConfiguration;
-        MemberConfiguration.Merge(configuration.Internal()?.MemberConfiguration);
+        if(configuration == null)
+        {
+            MemberConfiguration.SourceNamingConvention ??= PascalCaseNamingConvention.Instance;
+            MemberConfiguration.DestinationNamingConvention ??= PascalCaseNamingConvention.Instance;
+        }
+        else
+        {
+            MemberConfiguration.Merge(configuration.Internal().MemberConfiguration);
+        }
         var globalIgnores = profile.GlobalIgnores.Concat(globalProfile?.GlobalIgnores);
         GlobalIgnores = globalIgnores == Array.Empty<string>() ? EmptyHashSet : new HashSet<string>(globalIgnores);
         SourceExtensionMethods = profile.SourceExtensionMethods.Concat(globalProfile?.SourceExtensionMethods).ToArray();
diff --git a/src/UnitTests/Bug/NamingConventions.cs b/src/UnitTests/Bug/NamingConventions.cs
index b10629bb0a..1344b0c8d8 100644
--- a/src/UnitTests/Bug/NamingConventions.cs
+++ b/src/UnitTests/Bug/NamingConventions.cs
@@ -67,7 +67,7 @@ public class Dario
     public string JaSeZovemImenom { get; set; }
 }
 
-public class When_mapping_with_lowercae_naming_conventions_two_ways_in_profiles : AutoMapperSpecBase
+public class When_mapping_with_lowercase_naming_conventions_two_ways_in_profiles : AutoMapperSpecBase
 {
     private Dario _dario;
     private Neda _neda;
@@ -98,6 +98,46 @@ public void Should_map_from_lower_to_pascal()
         _neda.ja_se_zovem_imenom.ShouldBe("foo");
     }
 
+    [Fact]
+    public void Should_map_from_pascal_to_lower()
+    {
+        _dario.JaSeZovemImenom.ShouldBe("foo");
+    }
+}
+
+public class When_mapping_with_lowercase_naming_conventions_two_ways : AutoMapperSpecBase
+{
+    private Dario _dario;
+    private Neda _neda;
+
+    protected override MapperConfiguration CreateConfiguration() => new(cfg =>
+    {
+        cfg.SourceMemberNamingConvention = new LowerUnderscoreNamingConvention();
+        cfg.DestinationMemberNamingConvention = new LowerUnderscoreNamingConvention();
+        cfg.CreateProfile("MyMapperProfile", prf =>
+        {
+            prf.DestinationMemberNamingConvention = PascalCaseNamingConvention.Instance;
+            prf.CreateMap<Neda, Dario>();
+        });
+        cfg.CreateProfile("MyMapperProfile2", prf =>
+        {
+            prf.SourceMemberNamingConvention = PascalCaseNamingConvention.Instance;
+            prf.CreateMap<Dario, Neda>();
+        });
+    });
+
+    protected override void Because_of()
+    {
+        _dario = Mapper.Map<Neda, Dario>(new Neda { ja_se_zovem_imenom = "foo" });
+        _neda = Mapper.Map<Dario, Neda>(_dario);
+    }
+
+    [Fact]
+    public void Should_map_from_lower_to_pascal()
+    {
+        _neda.ja_se_zovem_imenom.ShouldBe("foo");
+    }
+
     [Fact]
     public void Should_map_from_pascal_to_lower()
     {