diff --git a/lib/ceedling/configurator.rb b/lib/ceedling/configurator.rb
index 2d78c2dc..b4a4a077 100644
--- a/lib/ceedling/configurator.rb
+++ b/lib/ceedling/configurator.rb
@@ -92,18 +92,43 @@ def merge_tools_defaults(config, default_config)
     msg = @reportinator.generate_progress( 'Collecting default tool configurations' )
     @loginator.log( msg, Verbosity::OBNOXIOUS )
 
-    # config[:project] is guaranteed to exist / validated to exist
+    # config[:project] is guaranteed to exist / validated to exist but may not include elements referenced below
     # config[:test_build] and config[:release_build] are optional in a user project configuration
-    release_assembly, _ = @config_walkinator.fetch_value( :release_build, :use_assembly, hash:config, default:false )
-    test_assembly, _ = @config_walkinator.fetch_value( :test_build, :use_assembly, hash:config, default:false)
+
+
+    release_build, _      = @config_walkinator.fetch_value( :project, :release_build, 
+                              hash:config,
+                              default: DEFAULT_CEEDLING_PROJECT_CONFIG[:project][:release_build]
+                            )
+
+    test_preprocessing, _ = @config_walkinator.fetch_value( :project, :use_test_preprocessor,
+                              hash:config,
+                              default: DEFAULT_CEEDLING_PROJECT_CONFIG[:project][:use_test_preprocessor]
+                            )
+
+    backtrace, _          = @config_walkinator.fetch_value( :project, :use_backtrace,
+                              hash:config,
+                              default: DEFAULT_CEEDLING_PROJECT_CONFIG[:project][:use_backtrace]
+                            )
+
+    release_assembly, _   = @config_walkinator.fetch_value( :release_build, :use_assembly,
+                              hash:config,
+                              default: DEFAULT_CEEDLING_PROJECT_CONFIG[:release_build][:use_assembly]
+                            )
+
+    test_assembly, _      = @config_walkinator.fetch_value( :test_build, :use_assembly,
+                              hash:config,
+                              default: DEFAULT_CEEDLING_PROJECT_CONFIG[:test_build][:use_assembly]
+                            )
 
     default_config.deep_merge( DEFAULT_TOOLS_TEST.deep_clone() )
 
-    default_config.deep_merge( DEFAULT_TOOLS_TEST_PREPROCESSORS.deep_clone() ) if (config[:project][:use_test_preprocessor] != :none)
+    default_config.deep_merge( DEFAULT_TOOLS_TEST_PREPROCESSORS.deep_clone() ) if (test_preprocessing != :none)
     default_config.deep_merge( DEFAULT_TOOLS_TEST_ASSEMBLER.deep_clone() )     if test_assembly
+    default_config.deep_merge( DEFAULT_TOOLS_TEST_GDB_BACKTRACE.deep_clone() ) if (backtrace == :gdb)
 
-    default_config.deep_merge( DEFAULT_TOOLS_RELEASE.deep_clone() )            if (config[:project][:release_build])
-    default_config.deep_merge( DEFAULT_TOOLS_RELEASE_ASSEMBLER.deep_clone() )  if (config[:project][:release_build] and release_assembly)
+    default_config.deep_merge( DEFAULT_TOOLS_RELEASE.deep_clone() )            if release_build
+    default_config.deep_merge( DEFAULT_TOOLS_RELEASE_ASSEMBLER.deep_clone() )  if (release_build and release_assembly)
   end
 
 
@@ -437,6 +462,7 @@ def eval_environment_variables(config)
 
       # Set the environment variable for our session
       @system_wrapper.env_set( key.to_s.upcase, hash[key] )
+      @loginator.log( " - #{key.to_s.upcase}: \"#{hash[key]}\"", Verbosity::DEBUG )
     end
   end
 
diff --git a/lib/ceedling/configurator_setup.rb b/lib/ceedling/configurator_setup.rb
index 3e41fb3d..ee06e742 100644
--- a/lib/ceedling/configurator_setup.rb
+++ b/lib/ceedling/configurator_setup.rb
@@ -171,14 +171,6 @@ def validate_tools(config)
       valid &= @configurator_validator.validate_tool( config:config, key:tool )
     end
 
-    if config[:project][:use_backtrace] == :gdb
-      valid &= @configurator_validator.validate_tool(
-        config:config,
-        key: :test_backtrace_gdb,
-        respect_optional: false
-      )
-    end
-
     return valid
   end
 
diff --git a/lib/ceedling/defaults.rb b/lib/ceedling/defaults.rb
index 9ae6e0f6..e7b1a71b 100644
--- a/lib/ceedling/defaults.rb
+++ b/lib/ceedling/defaults.rb
@@ -234,9 +234,7 @@
 DEFAULT_TEST_BACKTRACE_GDB_TOOL = {
   :executable => ENV['GDB'].nil? ? FilePathUtils.os_executable_ext('gdb').freeze : ENV['GDB'],
   :name => 'default_test_backtrace_gdb'.freeze,
-  # Must be optional because validation is contingent on backtrace configuration.
-  # (Don't break a build if `gdb` is unavailable but backtrace does not require it.)
-  :optional => true.freeze,
+  :optional => false.freeze,
   :arguments => [
     '-q'.freeze,
     '--batch'.freeze,
@@ -253,8 +251,13 @@
     :test_compiler => DEFAULT_TEST_COMPILER_TOOL,
     :test_linker   => DEFAULT_TEST_LINKER_TOOL,
     :test_fixture  => DEFAULT_TEST_FIXTURE_TOOL,
-    :test_fixture_simple_backtrace => DEFAULT_TEST_FIXTURE_SIMPLE_BACKTRACE_TOOL,
-    :test_backtrace_gdb => DEFAULT_TEST_BACKTRACE_GDB_TOOL,
+    :test_fixture_simple_backtrace => DEFAULT_TEST_FIXTURE_SIMPLE_BACKTRACE_TOOL
+    }
+  }
+
+DEFAULT_TOOLS_TEST_GDB_BACKTRACE = {
+  :tools => {
+    :test_backtrace_gdb => DEFAULT_TEST_BACKTRACE_GDB_TOOL
     }
   }