diff --git a/UnitsNet.Tests/UnitAbbreviationsCacheTests.cs b/UnitsNet.Tests/UnitAbbreviationsCacheTests.cs
index 5103231a36..5e83ae4d67 100644
--- a/UnitsNet.Tests/UnitAbbreviationsCacheTests.cs
+++ b/UnitsNet.Tests/UnitAbbreviationsCacheTests.cs
@@ -296,6 +296,28 @@ public void MapUnitToDefaultAbbreviation_GivenCustomAbbreviation_SetsAbbreviatio
             Assert.Equal("1 m^2", Area.FromSquareMeters(1).ToString(newZealandCulture));
         }
 
+        [Fact]
+        public void MapUnitToDefaultAbbreviation_ParsesUsingDefaultString()
+        {
+            var cache = new UnitAbbreviationsCache();
+            cache.MapUnitToDefaultAbbreviation(MassFlowUnit.GramPerSecond, NorwegianCulture, "grams/second");
+
+            var parser = new QuantityParser(cache);
+            Assert.Equal(MassFlow.FromPoundsPerSecond(10), parser.Parse<MassFlow, MassFlowUnit>("10 lb/s", NorwegianCulture, MassFlow.From));
+        }
+
+        [Fact]
+        public void MapUnitToDefaultAbbreviation_AddsNewUnitAsAdditionalOverride()
+        {
+            var cache = new UnitAbbreviationsCache();
+            var abbreviationsBefore = cache.GetUnitAbbreviations(MassFlowUnit.GramPerSecond, NorwegianCulture);
+
+            cache.MapUnitToDefaultAbbreviation(MassFlowUnit.GramPerSecond, NorwegianCulture, "grams/second");
+
+            var abbreviationsAfter = cache.GetUnitAbbreviations(MassFlowUnit.GramPerSecond, NorwegianCulture);
+            Assert.Equal(abbreviationsBefore.Length + 1, abbreviationsAfter.Length);
+        }
+
         /// <summary>
         ///     Convenience method to the proper culture parameter type.
         /// </summary>
diff --git a/UnitsNet/CustomCode/UnitAbbreviationsCache.cs b/UnitsNet/CustomCode/UnitAbbreviationsCache.cs
index a0b52ff101..dbb84304de 100644
--- a/UnitsNet/CustomCode/UnitAbbreviationsCache.cs
+++ b/UnitsNet/CustomCode/UnitAbbreviationsCache.cs
@@ -276,9 +276,11 @@ public string[] GetUnitAbbreviations(Type unitType, int unitValue, IFormatProvid
             if(!TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var lookup))
                 return formatProvider != FallbackCulture ? GetUnitAbbreviations(unitType, unitValue, FallbackCulture) : new string[] { };
 
-            var abbreviations = lookup!.GetAbbreviationsForUnit(unitValue);
-            if(abbreviations.Count == 0)
-                return formatProvider != FallbackCulture ? GetUnitAbbreviations(unitType, unitValue, FallbackCulture) : new string[] { };
+            var abbreviations = new HashSet<string>();
+            abbreviations.UnionWith(lookup!.GetAbbreviationsForUnit(unitValue));
+
+            if(formatProvider != FallbackCulture)
+                abbreviations.UnionWith(GetUnitAbbreviations(unitType, unitValue, FallbackCulture));
 
             return abbreviations.ToArray();
         }
@@ -297,10 +299,32 @@ public string[] GetAllUnitAbbreviationsForQuantity(Type unitEnumType, IFormatPro
             if(!TryGetUnitValueAbbreviationLookup(unitEnumType, formatProvider, out var lookup))
                 return formatProvider != FallbackCulture ? GetAllUnitAbbreviationsForQuantity(unitEnumType, FallbackCulture) : new string[] { };
 
-            return lookup!.GetAllUnitAbbreviationsForQuantity();
+            var allAbbreviations = new HashSet<string>();
+            allAbbreviations.UnionWith(lookup!.GetAllUnitAbbreviationsForQuantity());
+
+            if(formatProvider != FallbackCulture)
+                allAbbreviations.UnionWith(GetAllUnitAbbreviationsForQuantity(unitEnumType, FallbackCulture));
+
+            return allAbbreviations.ToArray();
+        }
+
+        internal List<int> GetUnitsForAbbreviation(Type unitType, IFormatProvider? formatProvider, string abbreviation, bool ignoreCase)
+        {
+            formatProvider = formatProvider ?? CultureInfo.CurrentUICulture;
+
+            if(!TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var lookup))
+                return formatProvider != FallbackCulture ? GetUnitsForAbbreviation(unitType, FallbackCulture, abbreviation, ignoreCase) : new List<int>();
+
+            var units = new HashSet<int>();
+            units.UnionWith(lookup!.GetUnitsForAbbreviation(abbreviation, ignoreCase));
+
+            if(formatProvider != FallbackCulture)
+                units.UnionWith(GetUnitsForAbbreviation(unitType, FallbackCulture, abbreviation, ignoreCase));
+
+            return units.ToList();
         }
 
-        internal bool TryGetUnitValueAbbreviationLookup(Type unitType, IFormatProvider? formatProvider, out UnitValueAbbreviationLookup? unitToAbbreviations)
+        private bool TryGetUnitValueAbbreviationLookup(Type unitType, IFormatProvider? formatProvider, out UnitValueAbbreviationLookup? unitToAbbreviations)
         {
             unitToAbbreviations = null;
 
diff --git a/UnitsNet/CustomCode/UnitParser.cs b/UnitsNet/CustomCode/UnitParser.cs
index 2becb1fd4d..9e8f95bcae 100644
--- a/UnitsNet/CustomCode/UnitParser.cs
+++ b/UnitsNet/CustomCode/UnitParser.cs
@@ -72,20 +72,17 @@ public Enum Parse([NotNull] string unitAbbreviation, Type unitType, IFormatProvi
             if (unitAbbreviation == null) throw new ArgumentNullException(nameof(unitAbbreviation));
             unitAbbreviation = unitAbbreviation.Trim();
 
-            if(!_unitAbbreviationsCache.TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var abbreviations))
-                throw new UnitNotFoundException($"No abbreviations defined for unit type [{unitType}] for culture [{formatProvider}].");
-
-            var unitIntValues = abbreviations!.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+            var unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: true);
 
             if (unitIntValues.Count == 0)
             {
                 unitAbbreviation = NormalizeUnitString(unitAbbreviation);
-                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+                unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: true);
             }
 
             // Narrow the search if too many hits, for example Megabar "Mbar" and Millibar "mbar" need to be distinguished
             if (unitIntValues.Count > 1)
-                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: false);
+                unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: false);
 
             switch (unitIntValues.Count)
             {
@@ -197,20 +194,17 @@ public bool TryParse(string? unitAbbreviation, Type unitType, IFormatProvider? f
             unitAbbreviation = unitAbbreviation.Trim();
             unit = default;
 
-            if(!_unitAbbreviationsCache.TryGetUnitValueAbbreviationLookup(unitType, formatProvider, out var abbreviations))
-                return false;
-
-            var unitIntValues = abbreviations!.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+            var unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: true);
 
             if (unitIntValues.Count == 0)
             {
                 unitAbbreviation = NormalizeUnitString(unitAbbreviation);
-                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: true);
+                unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: true);
             }
 
             // Narrow the search if too many hits, for example Megabar "Mbar" and Millibar "mbar" need to be distinguished
             if (unitIntValues.Count > 1)
-                unitIntValues = abbreviations.GetUnitsForAbbreviation(unitAbbreviation, ignoreCase: false);
+                unitIntValues = _unitAbbreviationsCache.GetUnitsForAbbreviation(unitType, formatProvider, unitAbbreviation, ignoreCase: false);
 
             if(unitIntValues.Count != 1)
                 return false;
diff --git a/UnitsNet/CustomCode/UnitValueAbbreviationLookup.cs b/UnitsNet/CustomCode/UnitValueAbbreviationLookup.cs
index a82d3f7faf..089770606a 100644
--- a/UnitsNet/CustomCode/UnitValueAbbreviationLookup.cs
+++ b/UnitsNet/CustomCode/UnitValueAbbreviationLookup.cs
@@ -73,7 +73,6 @@ internal void Add(int unit, string abbreviation, bool setAsDefault = false)
                 abbreviationsForUnit.Insert(0, abbreviation);
             else
                 abbreviationsForUnit.Add(abbreviation);
-
         }
     }
 }