diff --git a/v2/build/generators.jam b/v2/build/generators.jam
index 5500f4398..a87dab34e 100644
--- a/v2/build/generators.jam
+++ b/v2/build/generators.jam
@@ -58,6 +58,43 @@ if "--debug-generators" in [ modules.peek : ARGV ]
 }
 
 
+# Clears cached viable source target type information except for target types
+# and generators with all source types listed as viable. Should be called when
+# something invalidates those cached values by possibly causing some new source
+# types to become viable.
+#
+local rule invalidate-extendable-viable-source-target-type-cache ( )
+{
+    local generators-with-cached-source-types = $(.vstg-cached-generators) ;
+    .vstg-cached-generators = ;
+    for local gen in $(generators-with-cached-source-types)
+    {
+        if $(.vstg.$(gen)) = *
+        {
+            .vstg-cached-generators += $(gen) ;
+        }
+        else
+        {
+            .vstg.$(gen) = ;
+        }
+    }
+
+    local types-with-cached-source-types = $(.vst-cached-types) ;
+    .vst-cached-types = ;
+    for local type in $(types-with-cached-source-types)
+    {
+        if $(.vst.$(type)) = *
+        {
+            .vst-cached-types += $(gen) ;
+        }
+        else
+        {
+            .vst.$(type) = ;
+        }
+    }
+}
+
+
 # Outputs a debug message if generators debugging is on. Each element of
 # 'message' is checked to see if it is a class instance. If so, instead of the
 # value, the result of 'str' call is output.
@@ -643,6 +680,24 @@ rule register ( g )
         base = $(base:B) ;
     }
     .generators-for-toolset.$(base) += $(g) ;
+
+
+    # After adding a new generator that can construct new target types, we need
+    # to clear the related cached viable source target type information for
+    # constructing a specific target type or using a specific generator. Cached
+    # viable source target type lists affected by this are those containing any
+    # of the target types constructed by the new generator or any of their base
+    # target types.
+    #
+    # A more advanced alternative to clearing that cached viable source target
+    # type information would be to expand it with additional source types or
+    # even better - mark it as needing to be expanded on next use.
+    #
+    # For now we just clear all the cached viable source target type information
+    # that does not simply state 'all types' and may implement a more detailed
+    # algorithm later on if it becomes needed.
+
+    invalidate-extendable-viable-source-target-type-cache ;
 }
 
 
@@ -783,6 +838,7 @@ rule viable-source-types ( target-type )
     local key = .vst.$(target-type) ;
     if ! $($(key))
     {
+        .vst-cached-types += $(target-type) ;
         local v = [ viable-source-types-real $(target-type) ] ;
         if ! $(v)
         {
@@ -844,6 +900,7 @@ local rule viable-source-types-for-generator ( generator )
     local key = .vstg.$(generator) ;
     if ! $($(key))
     {
+        .vstg-cached-generators += $(generator) ;
         local v = [ viable-source-types-for-generator-real $(generator) ] ;
         if ! $(v)
         {
diff --git a/v2/test/generator_selection.py b/v2/test/generator_selection.py
new file mode 100755
index 000000000..192683ca7
--- /dev/null
+++ b/v2/test/generator_selection.py
@@ -0,0 +1,64 @@
+#!/usr/bin/python
+
+# Copyright 2008 Jurko Gospodnetic
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
+
+# Tests that generators get selected correctly.
+
+import BoostBuild
+
+
+################################################################################
+#
+# test_generator_added_after_already_building_a_target_of_its_target_type()
+# -------------------------------------------------------------------------
+#
+################################################################################
+
+def test_generator_added_after_already_building_a_target_of_its_target_type():
+    """Regression test for a Boost Build bug causing it to not use a generator
+    if it got added after already building a targer of its target type.
+    """
+
+    t = BoostBuild.Tester()
+
+    t.write("dummy.cpp", "void f() {}\n")
+
+    t.write("jamroot.jam", """
+# Building this dummy target must not cause a later defined CPP target type
+# generator not to be recognized as viable.
+obj dummy : dummy.cpp ;
+alias the-other-obj : Other//other-obj ;
+""")
+
+    t.write("Other/source.extension", "A dummy source file.")
+
+    t.write("Other/mygen.jam", """
+import generators ;
+import type ;
+type.register MY_TYPE : extension ;
+generators.register-standard mygen.generate-a-cpp-file : MY_TYPE : CPP ;
+rule generate-a-cpp-file { ECHO Generating a CPP file... ; }
+actions generate-a-cpp-file { echo void g() {} > "$(<)" }
+""")
+
+    t.write("Other/jamfile.jam", """
+import mygen ;
+obj other-obj : source.extension ;
+""")
+
+    t.run_build_system()
+    t.expect_output_line("Generating a CPP file...")
+
+    t.cleanup()
+
+
+################################################################################
+#
+# main()
+# ------
+#
+################################################################################
+
+test_generator_added_after_already_building_a_target_of_its_target_type()
diff --git a/v2/test/test_all.py b/v2/test/test_all.py
index 73f14a566..98b7fcbe5 100644
--- a/v2/test/test_all.py
+++ b/v2/test/test_all.py
@@ -171,7 +171,8 @@ tests = [ "rebuilds",
           "sort_rule",
           "ordered_include",
           "test_result_dumping",
-          "inherited_dependency"
+          "inherited_dependency",
+          "generator_selection"
           ]
 
 if os.name == 'posix':