Index: DamClients/DamUI/trunk/src/Dam/Deltares.Dam.Tests/StiImporter/SoilProfile2DImporterTest.cs
===================================================================
diff -u -r4285 -r4292
--- DamClients/DamUI/trunk/src/Dam/Deltares.Dam.Tests/StiImporter/SoilProfile2DImporterTest.cs	(.../SoilProfile2DImporterTest.cs)	(revision 4285)
+++ DamClients/DamUI/trunk/src/Dam/Deltares.Dam.Tests/StiImporter/SoilProfile2DImporterTest.cs	(.../SoilProfile2DImporterTest.cs)	(revision 4292)
@@ -168,7 +168,6 @@
         [Test]
         public void Import_WithIncompleteSoilList_ThrowsSoilProfileImporterException()
         {
-            // Setup
             const string invalidSoilProfile = "Tutorial-1a 10.1.4.3.sti"; // Soil profile also contains peat and sand for its layers
             const string profileName = "SimpleProfile";
             Segment segment = CreateSegmentWithProfiles(new[]
@@ -182,18 +181,13 @@
                 "Muck"
             });
 
-            // Call
-            TestDelegate call = () => SoilProfile2DImporter.Import(TestDataFolder, segment, availableSoils);
-
-            // Assert
-            Assert.That(call, Throws.Exception.TypeOf<SoilProfileImporterException>()
-                                    .With.Message.EqualTo($"'{invalidSoilProfile}' contains undefined soils."));
+            Assert.That(() => SoilProfile2DImporter.Import(TestDataFolder, segment, availableSoils), 
+                        Throws.Exception.TypeOf<SoilProfileImporterException>().With.Message.EqualTo($"'{invalidSoilProfile}' contains the undefined soil: Peat."));
         }
 
         [Test]
         public void Import_WithSoilProfileCausingReadException_ThrowsSoilProfileImporterException()
         {
-            // Setup
             const string invalidSoilProfileName = "NonExistentSoilProfile";
             Segment segment = CreateSegmentWithProfiles(new[]
             {
Index: DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/StiImporter/SoilProfile2DImporter.cs
===================================================================
diff -u -r4285 -r4292
--- DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/StiImporter/SoilProfile2DImporter.cs	(.../SoilProfile2DImporter.cs)	(revision 4285)
+++ DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/StiImporter/SoilProfile2DImporter.cs	(.../SoilProfile2DImporter.cs)	(revision 4292)
@@ -72,10 +72,11 @@
         {
             string profileName = profile.SoilGeometry2DName;
             SoilProfile2D readSoilProfile = ReadSoilProfile(soilProfileDirectory, profileName);
-            if (!IsValidSoilProfile(availableSoils, readSoilProfile))
+            string missingSoil = IsValidSoilProfile(availableSoils.Soils, readSoilProfile.Surfaces);
+            if (missingSoil != string.Empty)
             {
                 string messageFormat = LocalizationManager.GetTranslatedText(typeof(SoilProfile2DImporter), "ImportSoilProfileErrorUndefinedMaterials");
-                throw new SoilProfileImporterException(string.Format(messageFormat, profileName));
+                throw new SoilProfileImporterException(string.Format(messageFormat, profileName, missingSoil));
             }
 
             TransferSoilLayerProperties(readSoilProfile.Surfaces);
@@ -143,10 +144,19 @@
         return string.Equals(Path.GetExtension(profileName), ".sti", StringComparison.OrdinalIgnoreCase);
     }
 
-    private static bool IsValidSoilProfile(SoilList availableSoils, SoilProfile2D profile)
+    private static string IsValidSoilProfile(IEnumerable<Soil> availableSoils, IEnumerable<SoilLayer2D> surfaces)
     {
-        var soilNames = new HashSet<string>(availableSoils.Soils.Select(s => s.Name));
-        return profile.Surfaces.All(soilLayer => soilNames.Contains(soilLayer.Name));
+        var missingSoil = string.Empty;
+        var soilNames = new HashSet<string>(availableSoils.Select(s => s.Name));
+        foreach (string soilName in surfaces.Select(s => s.Soil.Name))
+        {
+            if (!soilNames.Contains(soilName))
+            {
+                missingSoil = soilName;
+            }
+        }
+
+        return missingSoil;
     }
 
     private static void TransferSoilLayerProperties(IEnumerable<SoilLayer2D> soilLayers)
Index: DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/Translations.xml
===================================================================
diff -u -r4256 -r4292
--- DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/Translations.xml	(.../Translations.xml)	(revision 4256)
+++ DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/Translations.xml	(.../Translations.xml)	(revision 4292)
@@ -827,8 +827,8 @@
     <Translation ID="ZoneTypeWarning"
                  en-US="The parameter Zone type will be set to 'No Zones' if 'Zone Areas' was selected."
                  nl-NL="De waarde voor Zone type wordt gezet naar 'Geen zones' als 'Zone gebieden' voorheen was geselecteerd."/>
-    <Translation ID="ImportSoilProfileErrorUndefinedMaterials" en-US="'{0}' contains undefined soils."
-                 nl-NL="'{0}' bevat ongedefinieerde materialen."/>
+    <Translation ID="ImportSoilProfileErrorUndefinedMaterials" en-US="'{0}' contains the undefined soil: {1}."
+                 nl-NL="'{0}' bevat het ongedefinieerde materiaal: {1}."/>
     <Translation ID="ImportSoilProfileErrorReadFailed" en-US="Could not import soil profile '{0}': {1}."
                  nl-NL="Kan grondprofiel '{0}' niet importeren: {1}."/>
     <Translation ID="ReadUnsupportedStiFile" en-US="'{0}' is an unsupported file."