diff --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -1682,6 +1682,34 @@
     m_breakpoint_list.UpdateBreakpoints(module_list, false, delete_locations);
     m_internal_breakpoint_list.UpdateBreakpoints(module_list, false,
                                                  delete_locations);
+
+    // If a module was torn down it will have torn down the 'TypeSystemClang's
+    // that we used as source 'ASTContext's for the persistent variables in
+    // the current target. Those would now be unsafe to access because the
+    // 'DeclOrigin' are now possibly stale. Thus clear all persistent
+    // variables. We only want to flush 'TypeSystem's if the module being
+    // unloaded was capable of describing a source type. JITted module unloads
+    // happen frequently for Objective-C utility functions or the REPL and rely
+    // on the persistent variables to stick around.
+    const bool should_flush_type_systems =
+        module_list.AnyOf([](lldb_private::Module &module) {
+          auto *object_file = module.GetObjectFile();
+
+          if (!object_file)
+            return false;
+
+          auto type = object_file->GetType();
+
+          // eTypeExecutable: when debugged binary was rebuilt
+          // eTypeSharedLibrary: if dylib was re-loaded
+          return module.FileHasChanged() &&
+                 (type == ObjectFile::eTypeObjectFile ||
+                  type == ObjectFile::eTypeExecutable ||
+                  type == ObjectFile::eTypeSharedLibrary);
+        });
+
+    if (should_flush_type_systems)
+      m_scratch_type_system_map.Clear();
   }
 }
 
diff --git a/lldb/test/API/functionalities/rerun_and_expr/Makefile b/lldb/test/API/functionalities/rerun_and_expr/Makefile
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr/Makefile
@@ -0,0 +1 @@
+include Makefile.rules
diff --git a/lldb/test/API/functionalities/rerun_and_expr/TestRerunAndExpr.py b/lldb/test/API/functionalities/rerun_and_expr/TestRerunAndExpr.py
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr/TestRerunAndExpr.py
@@ -0,0 +1,62 @@
+"""
+Test that re-running a process from within the same target
+after rebuilding the executable flushes the scratch TypeSystems
+tied to that process.
+"""
+
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestRerunExpr(TestBase):
+    def test(self):
+        """
+        Tests whether re-launching a process without destroying
+        the owning target keeps invalid ASTContexts in the
+        scratch AST's importer.
+
+        We test this by:
+        1. Evaluating an expression to import 'struct Foo' into
+           the scratch AST
+        2. Change the definition of 'struct Foo' and rebuild the executable
+        3. Re-launch the process
+        4. Evaluate the same expression in (1). We expect to have only
+           the latest definition of 'struct Foo' in the scratch AST.
+        """
+        self.build(dictionary={'CXX_SOURCES':'main.cpp', 'EXE':'a.out'})
+
+        exe = self.getBuildArtifact("a.out")
+        target = self.dbg.CreateTarget(exe) 
+        target.BreakpointCreateBySourceRegex('return', lldb.SBFileSpec('rebuild.cpp'))
+        target.BreakpointCreateBySourceRegex('return', lldb.SBFileSpec('main.cpp'))
+        process = target.LaunchSimple(None, None, self.get_process_working_directory())  
+
+        self.expect_expr('foo', result_type='Foo', result_children=[
+                ValueCheck(name='m_val', value='42')
+            ])
+
+        self.build(dictionary={'CXX_SOURCES':'rebuild.cpp', 'EXE':'a.out'})
+
+        # Rerun program within the same target
+        process.Destroy()
+        process = target.LaunchSimple(None, None, self.get_process_working_directory())  
+
+        self.expect_expr('foo', result_type='Foo', result_children=[
+            ValueCheck(name='Base', children=[
+                ValueCheck(name='m_base_val', value='42')
+            ]),
+            ValueCheck(name='m_derived_val', value='137')
+        ])
+
+        self.filecheck("target module dump ast", __file__)
+
+        # The new definition 'struct Foo' is in the scratch AST
+        # CHECK:      |-CXXRecordDecl {{.*}} struct Foo definition
+        # CHECK:      | |-public 'Base'
+        # CHECK-NEXT: | `-FieldDecl {{.*}} m_derived_val 'int'
+        # CHECK-NEXT: `-CXXRecordDecl {{.*}} struct Base definition
+        # CHECK:        `-FieldDecl {{.*}} m_base_val 'int'
+
+        # ...but the original definition of 'struct Foo' is not in the scratch AST anymore
+        # CHECK-NOT: FieldDecl {{.*}} m_val 'int'
+
diff --git a/lldb/test/API/functionalities/rerun_and_expr/main.cpp b/lldb/test/API/functionalities/rerun_and_expr/main.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr/main.cpp
@@ -0,0 +1,8 @@
+struct Foo {
+  int m_val = 42;
+};
+
+int main() {
+  Foo foo;
+  return 0;
+}
diff --git a/lldb/test/API/functionalities/rerun_and_expr/rebuild.cpp b/lldb/test/API/functionalities/rerun_and_expr/rebuild.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr/rebuild.cpp
@@ -0,0 +1,12 @@
+struct Base {
+  int m_base_val = 42;
+};
+
+struct Foo : public Base {
+  int m_derived_val = 137;
+};
+
+int main() {
+  Foo foo;
+  return 0;
+}
diff --git a/lldb/test/API/functionalities/rerun_and_expr_dylib/Makefile b/lldb/test/API/functionalities/rerun_and_expr_dylib/Makefile
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr_dylib/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/functionalities/rerun_and_expr_dylib/TestRerunAndExprDylib.py b/lldb/test/API/functionalities/rerun_and_expr_dylib/TestRerunAndExprDylib.py
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr_dylib/TestRerunAndExprDylib.py
@@ -0,0 +1,84 @@
+"""
+Test that re-running a process from within the same target
+after rebuilding the a dynamic library flushes the scratch
+TypeSystems tied to that process.
+"""
+
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+from lldbsuite.test.decorators import *
+
+class TestRerunExprDylib(TestBase):
+    @skipIfWindows
+    def test(self):
+        """
+        Tests whether re-launching a process without destroying
+        the owning target keeps invalid ASTContexts in the
+        scratch AST's importer.
+
+        We test this by:
+        1. Evaluating an expression to import 'struct Foo' into
+           the scratch AST
+        2. Change the definition of 'struct Foo' and rebuild the dylib
+        3. Re-launch the process
+        4. Evaluate the same expression in (1). We expect to have only
+           the latest definition of 'struct Foo' in the scratch AST.
+        """
+
+        DYLIB_NAME = 'foo'
+        FULL_DYLIB_NAME = 'libfoo.dylib' if self.platformIsDarwin() else 'libfoo.so'
+
+        # Build libfoo.dylib
+        self.build(dictionary={'DYLIB_CXX_SOURCES':'lib.cpp',
+                               'DYLIB_ONLY':'YES',
+                               'DYLIB_NAME':DYLIB_NAME,
+                               'USE_LIBDL':'1',
+                               'LD_EXTRAS':'-L.'})
+
+        # Build a.out
+        self.build(dictionary={'EXE':'a.out',
+                               'CXX_SOURCES':'main.cpp',
+                               'USE_LIBDL':'1',
+                               'CXXFLAGS_EXTRAS':f'-DLIB_NAME=\\"{FULL_DYLIB_NAME}\\"',
+                               'LD_EXTRAS':'-L.'})
+
+        exe = self.getBuildArtifact("a.out")
+        target = self.dbg.CreateTarget(exe) 
+        breakpoint = target.BreakpointCreateBySourceRegex('return', lldb.SBFileSpec('main.cpp'))
+        process = target.LaunchSimple(None, None, self.get_process_working_directory())  
+
+        self.expect_expr('*foo', result_type='Foo', result_children=[
+                ValueCheck(name='m_val', value='42')
+            ])
+
+        # Re-build libfoo.dylib
+        self.build(dictionary={'DYLIB_CXX_SOURCES':'rebuild.cpp',
+                               'DYLIB_ONLY':'YES',
+                               'DYLIB_NAME':DYLIB_NAME,
+                               'USE_LIBDL':'1',
+                               'LD_EXTRAS':'-L.'})
+
+        # Rerun program within the same target
+        process.Destroy()
+        process = target.LaunchSimple(None, None, self.get_process_working_directory())  
+
+        self.expect_expr('*foo', result_type='Foo', result_children=[
+            ValueCheck(name='Base', children=[
+                ValueCheck(name='m_base_val', value='42')
+            ]),
+            ValueCheck(name='m_derived_val', value='137')
+        ])
+
+        self.filecheck("target module dump ast", __file__)
+
+        # The new definition 'struct Foo' is in the scratch AST
+        # CHECK:      |-CXXRecordDecl {{.*}} struct Foo definition
+        # CHECK:      | |-public 'Base'
+        # CHECK-NEXT: | `-FieldDecl {{.*}} m_derived_val 'int'
+        # CHECK-NEXT: `-CXXRecordDecl {{.*}} struct Base definition
+        # CHECK:        `-FieldDecl {{.*}} m_base_val 'int'
+
+        # ...but the original definition of 'struct Foo' is not in the scratch AST anymore
+        # CHECK-NOT: FieldDecl {{.*}} m_val 'int'
+
diff --git a/lldb/test/API/functionalities/rerun_and_expr_dylib/lib.cpp b/lldb/test/API/functionalities/rerun_and_expr_dylib/lib.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr_dylib/lib.cpp
@@ -0,0 +1 @@
+LLDB_DYLIB_EXPORT struct Foo { int m_val = 42; } global_foo;
diff --git a/lldb/test/API/functionalities/rerun_and_expr_dylib/main.cpp b/lldb/test/API/functionalities/rerun_and_expr_dylib/main.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr_dylib/main.cpp
@@ -0,0 +1,17 @@
+#include <cassert>
+#include <dlfcn.h>
+#include <string>
+
+extern struct Foo imported;
+
+int main() {
+  // LIB_NAME defined on commandline
+  std::string libname{"./"};
+  libname += LIB_NAME;
+
+  void *handle = dlopen(libname.c_str(), RTLD_NOW);
+  struct Foo *foo = (struct Foo *)dlsym(handle, "global_foo");
+  assert(foo != nullptr);
+
+  return 0;
+}
diff --git a/lldb/test/API/functionalities/rerun_and_expr_dylib/rebuild.cpp b/lldb/test/API/functionalities/rerun_and_expr_dylib/rebuild.cpp
new file mode 100644
--- /dev/null
+++ b/lldb/test/API/functionalities/rerun_and_expr_dylib/rebuild.cpp
@@ -0,0 +1,7 @@
+struct Base {
+  int m_base_val = 42;
+};
+
+LLDB_DYLIB_EXPORT struct Foo : public Base {
+  int m_derived_val = 137;
+} global_foo;