diff --git a/compiler/main/HscTypes.hs b/compiler/main/HscTypes.hs
index 02592a3c14803e67cef0a9c6ad13d6bdab6c2c5a..dfc394d715769862b01f470ec128afcac81ce50d 100644
--- a/compiler/main/HscTypes.hs
+++ b/compiler/main/HscTypes.hs
@@ -1588,15 +1588,14 @@ mkQualPackage dflags pkg_key
         -- Skip the lookup if it's main, since it won't be in the package
         -- database!
      = False
-     | searchPackageId dflags pkgid `lengthIs` 1
+     | Just pkgid <- mb_pkgid
+     , searchPackageId dflags pkgid `lengthIs` 1
         -- this says: we are given a package pkg-0.1@MMM, are there only one
         -- exposed packages whose package ID is pkg-0.1?
      = False
      | otherwise
      = True
-     where pkg = fromMaybe (pprPanic "qual_pkg" (ftext (packageKeyFS pkg_key)))
-                    (lookupPackage dflags pkg_key)
-           pkgid = sourcePackageId pkg
+     where mb_pkgid = fmap sourcePackageId (lookupPackage dflags pkg_key)
 
 -- | A function which only qualifies package names if necessary; but
 -- qualifies all other identifiers.