diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 83cdf13a6..eeb237839 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -871,7 +871,12 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
 
 void LocalStore::autoGC(bool sync)
 {
-    auto getAvail = [this]() {
+    static auto fakeFreeSpaceFile = getEnv("_NIX_TEST_FREE_SPACE_FILE", "");
+
+    auto getAvail = [this]() -> uint64_t {
+        if (!fakeFreeSpaceFile.empty())
+            return std::stoll(readFile(fakeFreeSpaceFile));
+
         struct statvfs st;
         if (statvfs(realStoreDir.c_str(), &st))
             throw SysError("getting filesystem info about '%s'", realStoreDir);
@@ -892,7 +897,7 @@ void LocalStore::autoGC(bool sync)
 
         auto now = std::chrono::steady_clock::now();
 
-        if (now < state->lastGCCheck + std::chrono::seconds(5)) return;
+        if (now < state->lastGCCheck + std::chrono::seconds(settings.minFreeCheckInterval)) return;
 
         auto avail = getAvail();
 
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 0af8215d1..0c0a9ec54 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -342,6 +342,9 @@ public:
     Setting<uint64_t> maxFree{this, std::numeric_limits<uint64_t>::max(), "max-free",
         "Stop deleting garbage when free disk space is above the specified amount."};
 
+    Setting<uint64_t> minFreeCheckInterval{this, 5, "min-free-check-interval",
+        "Number of seconds between checking free disk space."};
+
     Setting<Paths> pluginFiles{this, {}, "plugin-files",
         "Plugins to dynamically load at nix initialization time."};
 };
diff --git a/tests/gc-auto.sh b/tests/gc-auto.sh
new file mode 100644
index 000000000..1e91282d0
--- /dev/null
+++ b/tests/gc-auto.sh
@@ -0,0 +1,59 @@
+source common.sh
+
+clearStore
+
+garbage1=$(nix add-to-store --name garbage1 ./tarball.sh)
+garbage2=$(nix add-to-store --name garbage2 ./tarball.sh)
+garbage3=$(nix add-to-store --name garbage3 ./tarball.sh)
+
+fake_free=$TEST_ROOT/fake-free
+export _NIX_TEST_FREE_SPACE_FILE=$fake_free
+echo 1100 > $fake_free
+
+expr=$(cat <<EOF
+with import ./config.nix; mkDerivation {
+  name = "gc-A";
+  buildCommand = ''
+    [[ \$(ls \$NIX_STORE/*-garbage? | wc -l) = 3 ]]
+    mkdir \$out
+    echo foo > \$out/bar
+    echo 1...
+    sleep 2
+    echo 100 > $fake_free
+    echo 2...
+    sleep 2
+    echo 3...
+    [[ \$(ls \$NIX_STORE/*-garbage? | wc -l) = 1 ]]
+  '';
+}
+EOF
+)
+
+nix build -o $TEST_ROOT/result-A -L "($expr)" \
+    --min-free 1000 --max-free 2000 --min-free-check-interval 1 &
+pid=$!
+
+expr2=$(cat <<EOF
+with import ./config.nix; mkDerivation {
+  name = "gc-B";
+  buildCommand = ''
+    mkdir \$out
+    echo foo > \$out/bar
+    echo 1...
+    sleep 2
+    echo 100 > $fake_free
+    echo 2...
+    sleep 2
+    echo 3...
+  '';
+}
+EOF
+)
+
+nix build -o $TEST_ROOT/result-B -L "($expr2)" \
+    --min-free 1000 --max-free 2000 --min-free-check-interval 1
+
+wait "$pid"
+
+[[ foo = $(cat $TEST_ROOT/result-A/bar) ]]
+[[ foo = $(cat $TEST_ROOT/result-B/bar) ]]
diff --git a/tests/local.mk b/tests/local.mk
index 1ff68348b..261e4db0d 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -3,7 +3,9 @@ check:
 
 nix_tests = \
   init.sh hash.sh lang.sh add.sh simple.sh dependencies.sh \
-  gc.sh gc-concurrent.sh \
+  gc.sh \
+  gc-concurrent.sh \
+  gc-auto.sh \
   referrers.sh user-envs.sh logging.sh nix-build.sh misc.sh fixed.sh \
   gc-runtime.sh check-refs.sh filter-source.sh \
   remote-store.sh export.sh export-graph.sh \