diff --git a/OMCompiler/Compiler/BackEnd/Unit.mo b/OMCompiler/Compiler/BackEnd/Unit.mo
index 2bd2e4c10b8..229561b83a7 100644
--- a/OMCompiler/Compiler/BackEnd/Unit.mo
+++ b/OMCompiler/Compiler/BackEnd/Unit.mo
@@ -563,6 +563,7 @@ end prefix2String;
 public function parseUnitString "author: lochel
   The second argument is optional."
   input String inUnitString;
+  input SourceInfo info;
   input HashTableStringToUnit.HashTable inKnownUnits = getKnownUnits();
   output Unit outUnit;
 protected
@@ -573,7 +574,7 @@ algorithm
   if listEmpty(charList) then
     fail();
   end if;
-  tokenList := lexer(charList);
+  tokenList := lexer(charList, info);
   outUnit := parser3({true, true}, tokenList, UNIT(1e0, 0, 0, 0, 0, 0, 0, 0), inKnownUnits);
   if not isUnit(outUnit) then
     fail();
@@ -809,6 +810,7 @@ end getPrefix;
 protected function lexer "author: lochel
   Tokenizer: charList to tokenList"
   input list<String> inCharList;
+  input SourceInfo info;
   output list<Token> outTokenList;
 algorithm
   outTokenList := matchcontinue(inCharList)
@@ -822,50 +824,50 @@ algorithm
     case {} then {};
 
     case "."::charList equation
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
     then T_MUL()::tokenList;
 
     case "("::charList equation
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
     then T_LPAREN()::tokenList;
 
     case ")"::charList equation
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
     then T_RPAREN()::tokenList;
 
     case "/"::charList equation
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
     then T_DIV()::tokenList;
 
     case "+"::charList equation
       (charList, number) = popNumber(charList);
       false = (number == "");
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
       i = stringInt(number);
     then T_NUMBER(i)::tokenList;
 
     case "-"::charList equation
       (charList, number) = popNumber(charList);
       false = (number == "");
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
       i = -stringInt(number);
     then T_NUMBER(i)::tokenList;
 
     case charList equation
       (charList, number) = popNumber(charList);
       false = (number == "");
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
       i = stringInt(number);
     then T_NUMBER(i)::tokenList;
 
     case charList equation
       (charList, unit) = popUnit(charList);
       false = (unit == "");
-      tokenList = lexer(charList);
+      tokenList = lexer(charList, info);
     then T_UNIT(unit)::tokenList;
 
     else equation
-      Error.addInternalError("function lexer failed", sourceInfo());
+      Error.addInternalError("function lexer failed: " + stringDelimitList(list("'" + c + "'" for c in inCharList), " "), info);
     then fail();
   end matchcontinue;
 end lexer;
diff --git a/OMCompiler/Compiler/BackEnd/UnitCheck.mo b/OMCompiler/Compiler/BackEnd/UnitCheck.mo
index 2c2fe3ea8be..4a820881fd5 100644
--- a/OMCompiler/Compiler/BackEnd/UnitCheck.mo
+++ b/OMCompiler/Compiler/BackEnd/UnitCheck.mo
@@ -995,7 +995,7 @@ algorithm
     guard(unitString <> "")
     equation
       cr = BackendVariable.varCref(var);
-      (ut, HtS2U, HtU2S) = parse(unitString, cr, HtS2U, HtU2S);
+      (ut, HtS2U, HtU2S) = parse(unitString, cr, var.source.info, HtS2U, HtU2S);
       HtCr2U = BaseHashTable.add((cr,ut),HtCr2U);
   then ((HtCr2U, HtS2U, HtU2S));
 
@@ -1016,6 +1016,7 @@ end convertUnitString2unit;
 protected function parse "author: lochel"
   input String inUnitString;
   input DAE.ComponentRef inCref;
+  input SourceInfo info;
   input HashTableStringToUnit.HashTable inHtS2U;
   input HashTableUnitToString.HashTable inHtU2S;
   output Unit.Unit outUnit;
@@ -1030,7 +1031,7 @@ algorithm
       then Unit.MASTER({inCref});
 
       case _
-      then Unit.parseUnitString(inUnitString, inHtS2U);
+      then Unit.parseUnitString(inUnitString, info, inHtS2U);
 
       else Unit.UNKNOWN(inUnitString);
     end matchcontinue;
diff --git a/OMCompiler/Compiler/SimCode/SimCodeUtil.mo b/OMCompiler/Compiler/SimCode/SimCodeUtil.mo
index 70fbf98d86d..3767576276b 100644
--- a/OMCompiler/Compiler/SimCode/SimCodeUtil.mo
+++ b/OMCompiler/Compiler/SimCode/SimCodeUtil.mo
@@ -8184,7 +8184,7 @@ algorithm
     deriv.comment := "der(" + deriv.comment + ")";
   end if;
   try
-    unit := Unit.parseUnitString(deriv.unit);
+    unit := Unit.parseUnitString(deriv.unit, state.source.info);
     unit := Unit.unitDiv(unit, Unit.UNIT(1e0, 0, 0, 0, 1, 0, 0, 0));
     deriv.unit := Unit.unitString(unit);
   else
@@ -9137,7 +9137,7 @@ algorithm
       if not stringEq(var.unit, "") and not BaseHashSet.has(var.unit, unitNameKeys) then
         unitNameKeys := BaseHashSet.add(var.unit, unitNameKeys);
         try
-          unit := Unit.parseUnitString(var.unit); // get the SI- units information
+          unit := Unit.parseUnitString(var.unit, var.source.info); // get the SI- units information
           unitDefinitions := SimCode.UNITDEFINITION(var.unit, transformUnitToBaseUnit(unit)) :: unitDefinitions;
         else
           // catch the units which are not calculated