diff --git a/CHANGELOG.md b/CHANGELOG.md
index b89a4714..a8d76039 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## 0.11
 
+Improvements:
+
+- More wisely pass the modified environment variables, if present, from the pre/post-configure scripts to tasks and debugging options. [#540](https://github.com/microsoft/vscode-makefile-tools/issues/540), [#493](https://github.com/microsoft/vscode-makefile-tools/issues/493), [#554](https://github.com/microsoft/vscode-makefile-tools/issues/554)
+
 Bug Fixes:
 
 - Ensure that we append line endings, which fixes a recent regression. [#641](https://github.com/microsoft/vscode-makefile-tools/issues/641)
diff --git a/src/launch.ts b/src/launch.ts
index 43e60634..7538e7c8 100644
--- a/src/launch.ts
+++ b/src/launch.ts
@@ -230,7 +230,13 @@ export class Launcher implements vscode.Disposable {
       request: "launch",
       cwd: this.getLaunchTargetDirectory(),
       args,
-      env: util.mergeEnvironment(process.env as util.EnvironmentVariables),
+      // Only pass a defined environment if there are modified environment variables.
+      env:
+        Object.keys(util.modifiedEnvironmentVariables).length > 0
+          ? util.mergeEnvironment(
+              util.modifiedEnvironmentVariables as util.EnvironmentVariables
+            )
+          : undefined,
       program: this.getLaunchTargetPath(),
       MIMode: miMode,
       miDebuggerPath: miDebuggerPath,
diff --git a/src/make.ts b/src/make.ts
index d4e89d23..3efffb27 100644
--- a/src/make.ts
+++ b/src/make.ts
@@ -478,7 +478,13 @@ export async function doBuildTarget(
     }
 
     let myTaskOptions: vscode.ShellExecutionOptions = {
-      env: util.mergeEnvironment(process.env as util.EnvironmentVariables),
+      // Only pass a defined environment if there are modified environment variables.
+      env:
+        Object.keys(util.modifiedEnvironmentVariables).length > 0
+          ? util.mergeEnvironment(
+              util.modifiedEnvironmentVariables as util.EnvironmentVariables
+            )
+          : undefined,
       cwd,
     };
 
@@ -1090,6 +1096,12 @@ async function applyEnvironment(content: string | undefined): Promise<void> {
     if (eqPos !== -1) {
       let envVarName: string = line.substring(0, eqPos);
       let envVarValue: string = line.substring(eqPos + 1, line.length);
+
+      // Only save to the modified environment values if it's different than the process.env.
+      if (!process.env[envVarName] || envVarValue !== process.env[envVarName]) {
+        util.modifiedEnvironmentVariables[envVarName] = envVarValue;
+      }
+
       process.env[envVarName] = envVarValue;
     }
   });
diff --git a/src/util.ts b/src/util.ts
index b8ba367e..752aacf3 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -338,6 +338,8 @@ export function mergeEnvironment(
   }, {});
 }
 
+export let modifiedEnvironmentVariables: EnvironmentVariables = {};
+
 export interface SpawnProcessResult {
   returnCode: number;
   signal: string;
@@ -388,6 +390,10 @@ export function spawnChildProcess(
         `integrated.automationShell.${shellPlatform}`
       ); // and replaced with automationProfile
 
+    if (typeof shellType === "object") {
+      shellType = shellType["path"];
+    }
+
     // Final quoting decisions for process name and args before being executed.
     let qProcessName: string = ensureQuoted
       ? quoteStringIfNeeded(processName)