Index: cross-project-tests/debuginfo-tests/dexter/dex/command/commands/DexUnreachable.py
===================================================================
--- cross-project-tests/debuginfo-tests/dexter/dex/command/commands/DexUnreachable.py
+++ cross-project-tests/debuginfo-tests/dexter/dex/command/commands/DexUnreachable.py
@@ -18,7 +18,21 @@
     See Commands.md for more info.
     """
 
-    def __init(self):
+    def __init__(self, *args, **kwargs):
+        if len(args) != 0:
+            raise TypeError("DexUnreachable takes no positional arguments")
+        if 'on_line' in kwargs:
+            on_line = kwargs.pop('on_line')
+            self._from_line = on_line
+            self._to_line = on_line
+        elif 'from_line' in kwargs and 'to_line' in kwargs:
+            self._from_line = kwargs.pop('from_line')
+            self._to_line = kwargs.pop('to_line')
+        elif 'from_line' in kwargs or 'to_line' in kwargs:
+            raise TypeError("Must provide both from_line and to_line to DexUnreachable")
+
+        if len(kwargs) > 0:
+            raise TypeError("Unexpected kwargs {}".format(kwargs.keys()))
         super(DexUnreachable, self).__init__()
         pass
 
Index: cross-project-tests/debuginfo-tests/dexter/dex/debugger/DebuggerControllers/ControllerHelpers.py
===================================================================
--- cross-project-tests/debuginfo-tests/dexter/dex/debugger/DebuggerControllers/ControllerHelpers.py
+++ cross-project-tests/debuginfo-tests/dexter/dex/debugger/DebuggerControllers/ControllerHelpers.py
@@ -18,6 +18,15 @@
     return any(os.path.samefile(step_info.current_location.path, f) \
                for f in source_files)
 
+def have_hit_line(watch, loc):
+  if watch.lineno == loc.lineno:
+    return True
+  elif hasattr(watch, '_on_line') and watch._on_line == loc.lineno:
+    return True
+  elif hasattr(watch, '_from_line') and watch._from_line <= loc.lineno and watch._to_line >= loc.lineno:
+    return True
+  return False
+
 def update_step_watches(step_info, watches, commands):
     watch_cmds = ['DexUnreachable', 'DexExpectStepOrder']
     towatch = chain.from_iterable(commands[x]
@@ -30,7 +39,7 @@
             if (loc.path != None
                     and os.path.exists(loc.path)
                     and os.path.samefile(watch.path, loc.path)
-                    and watch.lineno == loc.lineno):
+                    and have_hit_line(watch, loc)):
                 result = watch.eval(step_info)
                 step_info.watches.update(result)
                 break
Index: cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/penalty/unreachable_line_range.cpp
===================================================================
--- /dev/null
+++ cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/penalty/unreachable_line_range.cpp
@@ -0,0 +1,17 @@
+// Purpose:
+//      Check that \DexUnreachable correctly applies a penalty if the command
+//      line is stepped on.
+//
+// UNSUPPORTED: system-darwin
+//
+//
+// RUN: not %dexter_regression_test -- %s | FileCheck %s
+// CHECK: unreachable_line_range.cpp:
+
+int
+main()
+{ // DexLabel('begin')
+  return 1;
+} // DexLabel('end')
+
+// DexUnreachable(from_line=ref('begin'), to_line=ref('end'))
Index: cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/penalty/unreachable_on_line.cpp
===================================================================
--- /dev/null
+++ cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/penalty/unreachable_on_line.cpp
@@ -0,0 +1,17 @@
+// Purpose:
+//      Check that \DexUnreachable correctly applies a penalty if the command
+//      line is stepped on.
+//
+// UNSUPPORTED: system-darwin
+//
+//
+// RUN: not %dexter_regression_test -- %s | FileCheck %s
+// CHECK: unreachable_on_line.cpp:
+
+int
+main()
+{
+  return 1;  // DexLabel('this_one')
+}
+
+// DexUnreachable(on_line=ref('this_one'))
Index: cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/perfect/unreachable_on_line.cpp
===================================================================
--- /dev/null
+++ cross-project-tests/debuginfo-tests/dexter/feature_tests/commands/perfect/unreachable_on_line.cpp
@@ -0,0 +1,18 @@
+// Purpose:
+//    Check that \DexUnreachable has no effect if the command line is never
+//    stepped on.
+//
+// UNSUPPORTED: system-darwin
+//
+// RUN: %dexter_regression_test -- %s | FileCheck %s
+// CHECK: unreachable_on_line.cpp:
+
+int main()
+{
+  return 0;
+  return 1; // DexLabel('this_one')
+}
+
+
+// DexUnreachable(on_line=ref('this_one'))
+// DexUnreachable(from_line=ref('this_one'), to_line=ref('this_one'))