diff --git a/src/libstore/build/derivation-building-goal.cc b/src/libstore/build/derivation-building-goal.cc
index d07beb9ec..025e995f2 100644
--- a/src/libstore/build/derivation-building-goal.cc
+++ b/src/libstore/build/derivation-building-goal.cc
@@ -155,6 +155,12 @@ Goal::Co DerivationBuildingGoal::gaveUpOnSubstitution(bool storeDerivation)
 
     /* Determine the full set of input paths. */
 
+    /**
+     * All input paths (that is, the union of FS closures of the
+     * immediate input paths).
+     */
+    StorePathSet inputPaths;
+
     if (storeDerivation) {
         assert(drv->inputDrvs.map.empty());
         /* Store the resolved derivation, as part of the record of
@@ -348,7 +354,7 @@ tryToBuild:
         if (buildLocally) {
             useHook = false;
         } else {
-            switch (tryBuildHook(initialOutputs)) {
+            switch (tryBuildHook(inputPaths, initialOutputs)) {
             case rpAccept:
                 /* Yes, it has started doing so.  Wait until we get
                    EOF from the hook. */
@@ -801,7 +807,8 @@ BuildError DerivationBuildingGoal::fixupBuilderFailureErrorMessage(BuilderFailur
     return BuildError{e.status, msg};
 }
 
-HookReply DerivationBuildingGoal::tryBuildHook(const std::map<std::string, InitialOutput> & initialOutputs)
+HookReply DerivationBuildingGoal::tryBuildHook(
+    const StorePathSet & inputPaths, const std::map<std::string, InitialOutput> & initialOutputs)
 {
 #ifdef _WIN32 // TODO enable build hook on Windows
     return rpDecline;
diff --git a/src/libstore/include/nix/store/build/derivation-building-goal.hh b/src/libstore/include/nix/store/build/derivation-building-goal.hh
index 1f2a57d86..ac5bd43f6 100644
--- a/src/libstore/include/nix/store/build/derivation-building-goal.hh
+++ b/src/libstore/include/nix/store/build/derivation-building-goal.hh
@@ -58,12 +58,6 @@ private:
      * The remainder is state held during the build.
      */
 
-    /**
-     * All input paths (that is, the union of FS closures of the
-     * immediate input paths).
-     */
-    StorePathSet inputPaths;
-
     /**
      * File descriptor for the log file.
      */
@@ -114,7 +108,8 @@ private:
     /**
      * Is the build hook willing to perform the build?
      */
-    HookReply tryBuildHook(const std::map<std::string, InitialOutput> & initialOutputs);
+    HookReply
+    tryBuildHook(const StorePathSet & inputPaths, const std::map<std::string, InitialOutput> & initialOutputs);
 
     /**
      * Open a log file and a pipe to it.