diff --git a/pom.xml b/pom.xml
index 8b7c7913d3f..1d000aa1593 100644
--- a/pom.xml
+++ b/pom.xml
@@ -456,7 +456,7 @@
         <dependency>
             <groupId>org.rascalmpl</groupId>
             <artifactId>typepal</artifactId>
-            <version>0.15.2-RC16</version>
+            <version>0.15.2-RC19</version>
            <!-- <scope>provided</scope> for shade plugin it can't be provided. At least the rascal dependency in typepal should be provided -->
            <scope>compile</scope>
         </dependency>
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/agrammar/definition/Characters.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/agrammar/definition/Characters.rsc
index 8e260a699cc..54698609b3d 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/agrammar/definition/Characters.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/agrammar/definition/Characters.rsc
@@ -38,7 +38,6 @@ extend lang::rascalcore::check::ATypeBase;
 import String;
 import List;
 
-//data AType;
 data ACharRange = \empty-range();
 
 ACharRange \new-range(int from, int to) = from <= to ? arange(from, to) : \empty-range();
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/BasicRascalConfig.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/BasicRascalConfig.rsc
index 420762d43a1..fbc76975909 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/BasicRascalConfig.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/BasicRascalConfig.rsc
@@ -148,9 +148,6 @@ data DefInfo(map[str,str] tags = ());
 // Function modifiers
 data DefInfo(list[str] modifiers = []);
 
-// Function md5Hash of source
-data DefInfo(str md5 = "");
-
 // Common Keyword fields for ADTs
 data DefInfo(list[KeywordFormal] commonKeywordFields = []);
 
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/Checker.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/Checker.rsc
index f4dc90debba..8b42be85c74 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/Checker.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/Checker.rsc
@@ -462,7 +462,7 @@ tuple[TModel, ModuleStatus] rascalTModelComponent(set[str] moduleNames, ModuleSt
 
         start_check = cpuTime();
         resetClosureCounter();
-        c = newCollector(modelName, namedTrees, compilerConfig);
+        c = newCollector(modelName, namedTrees, compilerConfig, timestamp = getLastModified(modelName, ms.moduleLastModified, pcfg));
         c.push(key_pathconfig, pcfg);
 
         rascalPreCollectInitialization(namedTrees, c);
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/CheckerCommon.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/CheckerCommon.rsc
index 14dea332912..9dbcc6836b5 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/CheckerCommon.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/CheckerCommon.rsc
@@ -431,24 +431,26 @@ ModuleStatus updatePaths(loc oldModuleLoc, loc newModuleLoc, ModuleStatus ms){
 }
 
 ModuleStatus consolidatePaths(ModuleStatus ms){
-    set[loc] locs = {lc| /loc lc := ms.paths};
-    map[loc,loc] lprops = ();
-    rel[loc,PathRole,loc] paths = ms.paths;
-    for(loc l <- locs){
-        if(l.top in lprops && loc r := lprops[l.top] && r != l){
-            if(l.length? && !r.length?){
-                paths = visit(paths) { case r: { insert l; }};
-            } else if(!l.length? && r.length?){
-                paths = visit(paths) { case l: { insert r; }};
-            } else {
-                mname = getRascalModuleName(l, ms.pathConfig);
-                causes = [info("Module location for <mname>: <x>", x) | x <- [l, r]];
-                ms.messages[mname] ? {} += { error("Conflicting module locations found for <mname>", l, causes=causes) };
-            }
-        }
-        lprops[l.top] = l;
-    }
-    ms.paths = paths;
+    // set[loc] locs = {lc| /loc lc := ms.paths};
+    // map[loc,loc] lprops = ();
+    // rel[loc,PathRole,loc] paths = ms.paths;
+    // for(loc l <- locs){
+    //     if(l.top in lprops && loc r := lprops[l.top] && r != l){
+    //         if(l.length? && !r.length?){
+    //             paths = visit(paths) { case r: { insert l; }};
+    //         } else if(!l.length? && r.length?){
+    //             paths = visit(paths) { case l: { insert r; }};
+    //         } else {
+    //             paths = visit(paths) { case l: { insert l.top; }};
+    //             // mname = getRascalModuleName(l, ms.pathConfig);
+    //             // causes = [info("Module location for <mname>: <x>", x) | x <- [l, r]];
+    //             // ms.messages[mname] ? {} += { error("Conflicting module locations found for <mname>", l, causes=causes) };
+    //         }
+    //     }
+    //     lprops[l.top] = l;
+    // }
+    // ms.paths = paths;
+    //ms.paths = visit(ms.paths) { case loc l => l.top };
 
     // strPaths = getStrPaths(ms.paths, ms.pathConfig);
     // if(strPaths != ms.strPaths){
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectDeclaration.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectDeclaration.rsc
index 10fb51abe9d..ea81a49777c 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectDeclaration.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectDeclaration.rsc
@@ -42,6 +42,7 @@ import lang::rascalcore::agrammar::definition::Attributes;
 import lang::rascalcore::check::SyntaxGetters;
 
 import lang::rascalcore::check::ATypeBase; // seemingly redundant
+extend lang::rascalcore::check::BasicRascalConfig;
 
 import IO;
 import List;
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectSyntaxDeclaration.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectSyntaxDeclaration.rsc
index 6a474472b4e..83b66455721 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectSyntaxDeclaration.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/CollectSyntaxDeclaration.rsc
@@ -40,6 +40,7 @@ import util::Maybe;
 import lang::rascalcore::agrammar::definition::Symbols;
 import lang::rascalcore::agrammar::definition::Attributes;
 import lang::rascalcore::check::ATypeBase; // seemingly redundant
+extend lang::rascalcore::check::BasicRascalConfig;
 
 // ---- syntax definition -----------------------------------------------------
 
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/RascalConfig.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/RascalConfig.rsc
index 8031643e163..2a6148ff925 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/RascalConfig.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/RascalConfig.rsc
@@ -31,8 +31,6 @@ module lang::rascalcore::check::RascalConfig
     High level configuration of the Rascal checker.
 */
 
-//import lang::rascalcore::check::CheckerCommon;
-
 import lang::rascalcore::check::ADTandGrammar;
 import lang::rascalcore::compile::muRascal::AST;
 
@@ -529,19 +527,19 @@ void rascalPostSolver(map[str,Tree] namedTrees, Solver s){
 // bool isLogicalLoc(loc l)
 //     = startsWith(l.scheme, "rascal+");
 
-loc rascalCreateLogicalLoc(Define def, str _modelName, PathConfig pcfg){
+tuple[bool, loc] rascalCreateLogicalLoc(Define def, str _modelName, PathConfig pcfg){
     if(def.idRole in keepInTModelRoles){
        if(isLogicalLoc(def.defined)) return def.defined;
        moduleName = getRascalModuleName(def.defined, pcfg);
        moduleNameSlashed = replaceAll(moduleName, "::", "/");
        suffix = def.defInfo.md5? ? "$<def.defInfo.md5[0..16]>" : "";
        if(def.idRole == moduleId()){
-            return |<"rascal+<prettyRole(def.idRole)>">:///<moduleNameSlashed><suffix>|;
+            return <true, |<"rascal+<prettyRole(def.idRole)>">:///<moduleNameSlashed><suffix>|>;
        } else {
-            return |<"rascal+<prettyRole(def.idRole)>">:///<moduleNameSlashed>/<reduceToURIChars(def.id)><suffix>|;
+            return <true, |<"rascal+<prettyRole(def.idRole)>">:///<moduleNameSlashed>/<reduceToURIChars(def.id)><suffix>|>;
        }
      }
-     return def.defined;
+     return <false, def.defined>;
 }
 
 @memo{expireAfter(minutes=5),maximumSize(1000)}
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/TestConfigs.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/TestConfigs.rsc
index 90508259e10..f1c268f9e19 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/TestConfigs.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/TestConfigs.rsc
@@ -50,6 +50,7 @@ public loc RASCAL        = |mvn://org.rascalmpl--rascal--0.41.0-RC15/|;
 public loc TYPEPAL       = |mvn://org.rascalmpl--typepal--0.14.8/|;
 public loc OUTDATED_TYPEPAL 
                   = |mvn://org.rascalmpl--typepal--0.14.1/|;
+public loc RASCAL_RC67   = |mvn://org.rascalmpl--rascal--0.41.0-RC67/|;
 
 public loc DRAMBIGUITY   = |mvn://org.rascalmpl--drambiguity--0.1.2/|;
 public loc FLYBYTES      = |mvn://org.rascalmpl--flybytes--0.1.5/|;
@@ -57,6 +58,7 @@ public loc SALIX_CORE    = |mvn://org.rascalmpl--salix-core--0.2.7/|;
 public loc SALIX_CONTRIB = |mvn://org.rascalmpl--salix-contrib--0.2.7/|;
 public loc RASCAL_LSP    = |mvn://org.rascalmpl--rascal-lsp--2.21.2/|;
 public loc PHP_ANALYSIS  = |mvn://org.rascalmpl--php-analysis--0.2.5-SNAPSHOT/|;
+public loc JAVA_AIR      = |mvn://org.rascalmpl--java-air--1.0.0-RC2/|;
 
 public loc REPO          =  |file:///Users/paulklint/git/|;
 public loc COMPILED_RASCAL 
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/BinaryDependencyTests.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/BinaryDependencyTests.rsc
index 31511550942..dc3126f40a4 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/BinaryDependencyTests.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/BinaryDependencyTests.rsc
@@ -403,6 +403,27 @@ test bool incompatibleVersionsOfBinaryLibrary(){
     // Recompile Check and discover the error
     return checkExpectErrors("Check", ["Review of dependencies, reconfiguration or recompilation needed: binary module `TP` depends (indirectly) on incompatible module(s)"], core.pcfg, remove = [rascal, typepal, core]);
 }
+@ignore{Unclear whether it should fail or succeed}
+test bool mixedRascalVersions() {
+    // This test project has a dependency on:
+    // * Rascal 0.41.0-RC67
+    // * java-air 1.0.0-RC2, which was built using Rascal 0.41.0-RC35
+    // The test module imports:
+    // * a standard library module from 0.41.0-RC67
+    // * a library module of which the packaged tpl was built using 0.41.0-RC35
+    clearMemory();
+    project_name = "test-project";
+    test_project =
+        createProject(
+            project_name,
+            ("Test": "import IO;
+                     'import lang::java::m3::Core;"),
+            createPathConfig(project_name)
+                    [libs=[RASCAL_RC67, JAVA_AIR]]
+                    [srcs=[src(project_name)]]
+                );
+    return checkExpectNoErrors("Test", test_project.pcfg, remove = [test_project]);
+}
 
 // ---- Binary compatibility of two TModels -----------------------------------
 
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/StaticTestingUtils.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/StaticTestingUtils.rsc
index 5f4c03fdb88..6dc2017f1c4 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/StaticTestingUtils.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/StaticTestingUtils.rsc
@@ -193,17 +193,17 @@ bool validateUseDefs(str moduleName, map[str, tuple[int, set[int]]] usedefs, Mod
 	println("names:"); iprintln(names);
 	<found, tm, ms> = getTModelForModule(moduleName, ms);
 	foundUseDefs = tm.useDef;
-	println("foundUseDefs:");
-	for(<u, d> <- foundUseDefs){
-		println("<readFile(u)>:<u> ==\> <d>");
-	}
+	// println("foundUseDefs:");
+	// for(<u, d> <- foundUseDefs){
+	// 	println("<readFile(u)>:<u> ==\> <d>");
+	// }
 	for(str v <- usedefs){
 		 <def, uses> = usedefs[v];
 		 list[loc] occ = [];
 		 if(names[v]?) occ = names[v]; else throw "<v> not found in tree";
 		 if(!occ[def]?) throw "Missing define <def> for <v>";
 		 for(int u <- uses){
-			println("u = <u>");
+			//println("u = <u>");
 			if(!occ[u]?){
 				throw "Missing use <u> for <v>";
 			}
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/download-test-jars.sh b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/download-test-jars.sh
index 5627b4b0c26..2e11565378e 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/download-test-jars.sh
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/check/tests/download-test-jars.sh
@@ -8,10 +8,12 @@ function download() {
 
 # these should be synced with `TestConfigs.rsc`
 download "org.rascalmpl" "rascal" "0.41.0-RC15" 
+download "org.rascalmpl" "rascal" "0.41.0-RC67"
 download "org.rascalmpl" "typepal" "0.14.8" 
 download "org.rascalmpl" "typepal" "0.14.1" 
 download "org.rascalmpl" "drambiguity" "0.1.2" 
 download "org.rascalmpl" "flybytes" "0.1.5" 
 download "org.rascalmpl" "salix-core" "0.2.7" 
 download "org.rascalmpl" "salix-contrib" "0.2.7" 
-download "org.rascalmpl" "rascal-lsp" "2.21.2" 
\ No newline at end of file
+download "org.rascalmpl" "rascal-lsp" "2.21.2" 
+download "org.rascalmpl" "java-air" "1.0.0-RC2"
\ No newline at end of file
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/JGenie.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/JGenie.rsc
index 84c3c961ae9..76c6339c543 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/JGenie.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/JGenie.rsc
@@ -91,6 +91,7 @@ JGenie makeJGenie(MuModule m,
                   
     map[str,loc] allModuleLocs = moduleLocs;
     map[loc,str] allLocs2Module = invertUnique(moduleLocs);
+    allLocs2Module += (l.top : allLocs2Module[l] | l <- domain(allLocs2Module) );
     MuModule currentModule = m;
     str moduleName = m.name;
     map[AType, map[str,AType]] commonKeywordFieldsNameAndType = m.commonKeywordFields;
diff --git a/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/Resolvers.rsc b/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/Resolvers.rsc
index 9cfda02bd34..719f692ffb0 100644
--- a/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/Resolvers.rsc
+++ b/src/org/rascalmpl/compiler/lang/rascalcore/compile/muRascal2Java/Resolvers.rsc
@@ -151,8 +151,8 @@ public set[set[Define]] mygroup(set[Define] input, bool (Define a, Define b) sim
 str generateResolvers(str moduleName, map[loc, MuFunction] loc2muFunction, set[str] imports, set[str] extends, map[str,TModel] tmodels, map[str,loc] module2loc, PathConfig pcfg, JGenie jg){
     module_scope = module2loc[moduleName];
 
-    loc2module = invertUnique(module2loc);
-    module_scopes = domain(loc2module);
+    map[loc,str] loc2module = invertUnique(module2loc);
+    set[loc] module_scopes = domain(loc2module);
     extend_scopes = { module2loc[ext] | ext <- extends, ext in module2loc};
     import_scopes = { module2loc[imp] | imp <- imports, imp in module2loc };
 
@@ -376,7 +376,7 @@ str generateResolver(str moduleName, str functionName, set[Define] fun_defs, map
     map[int, lrel[str,str]] overload_table = ();
     lrel[str,str] defaults_and_constructors = [];
 
-    physical2logical = invertUnique(tm.logical2physical);
+    map[loc,loc] physical2logical = invertUnique(tm.logical2physical);
 
     // Handle a function or constructor defintion