diff --git a/ChangeLog.md b/ChangeLog.md
index 6e6ef4e0db..2d205a387c 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -22,6 +22,8 @@ Bug fixes:
   [#5545](https://github.com/commercialhaskell/stack/issues/5545)
 * Bump `pantry` version for better OS support. See
   [pantry#33](https://github.com/commercialhaskell/pantry/issues/33)
+* When building the sanity check for a new GHC install, make sure to clear
+  `GHC_PACKAGE_PATH`.
 
 
 ## v2.7.1
diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
index d56262a4bf..a22b0ef346 100644
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -673,9 +673,16 @@ ensureSandboxedCompiler sopts getSetupInfo' = do
           case res of
             Left _ -> loop xs
             Right y -> parseAbsFile y
-    compiler <- withProcessContext menv $ loop names
+    compiler <- withProcessContext menv $ do
+      compiler <- loop names
+
+      -- Run this here to ensure that the sanity check uses the modified
+      -- environment, otherwise we may infect GHC_PACKAGE_PATH and break sanity
+      -- checks.
+      when (soptsSanityCheck sopts) $ sanityCheck compiler
+
+      pure compiler
 
-    when (soptsSanityCheck sopts) $ sanityCheck compiler
     cp <- pathsFromCompiler wc compilerBuild True compiler
     pure (cp, paths)