diff --git a/src/hydra-eval-jobs/Makefile.am b/src/hydra-eval-jobs/Makefile.am
index c31849d9..7a4e9c91 100644
--- a/src/hydra-eval-jobs/Makefile.am
+++ b/src/hydra-eval-jobs/Makefile.am
@@ -2,5 +2,4 @@ bin_PROGRAMS = hydra-eval-jobs
 
 hydra_eval_jobs_SOURCES = hydra-eval-jobs.cc
 hydra_eval_jobs_LDADD = $(NIX_LIBS)
-
-AM_CXXFLAGS = $(NIX_CFLAGS)
+hydra_eval_jobs_CXXFLAGS = $(NIX_CFLAGS) -I ../libhydra
diff --git a/src/hydra-eval-jobs/hydra-eval-jobs.cc b/src/hydra-eval-jobs/hydra-eval-jobs.cc
index 1e17e99d..d6f82276 100644
--- a/src/hydra-eval-jobs/hydra-eval-jobs.cc
+++ b/src/hydra-eval-jobs/hydra-eval-jobs.cc
@@ -13,6 +13,8 @@
 #include "globals.hh"
 #include "common-eval-args.hh"
 
+#include "hydra-config.hh"
+
 using namespace nix;
 
 
@@ -157,6 +159,13 @@ int main(int argc, char * * argv)
     unsetenv("NIX_PATH");
 
     return handleExceptions(argv[0], [&]() {
+
+        auto config = std::make_unique<::Config>();
+
+        auto initialHeapSize = config->getStrOption("evaluator_initial_heap_size", "");
+        if (initialHeapSize != "")
+            setenv("GC_INITIAL_HEAP_SIZE", initialHeapSize.c_str(), 1);
+
         initNix();
         initGC();
 
diff --git a/src/hydra-queue-runner/hydra-queue-runner.cc b/src/hydra-queue-runner/hydra-queue-runner.cc
index eec51770..70329a9e 100644
--- a/src/hydra-queue-runner/hydra-queue-runner.cc
+++ b/src/hydra-queue-runner/hydra-queue-runner.cc
@@ -10,10 +10,11 @@
 #include "store-api.hh"
 #include "remote-store.hh"
 
-#include "shared.hh"
 #include "globals.hh"
+#include "hydra-config.hh"
 #include "json.hh"
 #include "s3-binary-cache-store.hh"
+#include "shared.hh"
 
 using namespace nix;
 
@@ -27,52 +28,6 @@ template<> void toJSON<double>(std::ostream & str, const double & n) { str << n;
 }
 
 
-struct Config
-{
-    std::map<std::string, std::string> options;
-
-    Config()
-    {
-        /* Read hydra.conf. */
-        auto hydraConfigFile = getEnv("HYDRA_CONFIG");
-        if (pathExists(hydraConfigFile)) {
-
-            for (auto line : tokenizeString<Strings>(readFile(hydraConfigFile), "\n")) {
-                line = trim(string(line, 0, line.find('#')));
-
-                auto eq = line.find('=');
-                if (eq == std::string::npos) continue;
-
-                auto key = trim(std::string(line, 0, eq));
-                auto value = trim(std::string(line, eq + 1));
-
-                if (key == "") continue;
-
-                options[key] = value;
-            }
-        }
-    }
-
-    std::string getStrOption(const std::string & key, const std::string & def = "")
-    {
-        auto i = options.find(key);
-        return i == options.end() ? def : i->second;
-    }
-
-    uint64_t getIntOption(const std::string & key, uint64_t def = 0)
-    {
-        auto i = options.find(key);
-        return i == options.end() ? def : std::stoll(i->second);
-    }
-
-    bool getBoolOption(const std::string & key, bool def = false)
-    {
-        auto i = options.find(key);
-        return i == options.end() ? def : (i->second == "true" || i->second == "1");
-    }
-};
-
-
 static uint64_t getMemSize()
 {
     auto pages = sysconf(_SC_PHYS_PAGES);
diff --git a/src/libhydra/hydra-config.hh b/src/libhydra/hydra-config.hh
new file mode 100644
index 00000000..a4050666
--- /dev/null
+++ b/src/libhydra/hydra-config.hh
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <map>
+
+#include "util.hh"
+
+struct Config
+{
+    std::map<std::string, std::string> options;
+
+    Config()
+    {
+        using namespace nix;
+
+        /* Read hydra.conf. */
+        auto hydraConfigFile = getEnv("HYDRA_CONFIG");
+        if (pathExists(hydraConfigFile)) {
+
+            for (auto line : tokenizeString<Strings>(readFile(hydraConfigFile), "\n")) {
+                line = trim(string(line, 0, line.find('#')));
+
+                auto eq = line.find('=');
+                if (eq == std::string::npos) continue;
+
+                auto key = trim(std::string(line, 0, eq));
+                auto value = trim(std::string(line, eq + 1));
+
+                if (key == "") continue;
+
+                options[key] = value;
+            }
+        }
+    }
+
+    std::string getStrOption(const std::string & key, const std::string & def = "")
+    {
+        auto i = options.find(key);
+        return i == options.end() ? def : i->second;
+    }
+
+    uint64_t getIntOption(const std::string & key, uint64_t def = 0)
+    {
+        auto i = options.find(key);
+        return i == options.end() ? def : std::stoll(i->second);
+    }
+
+    bool getBoolOption(const std::string & key, bool def = false)
+    {
+        auto i = options.find(key);
+        return i == options.end() ? def : (i->second == "true" || i->second == "1");
+    }
+};