diff --git a/js/src/jit-test/tests/gc/bug-1138390.js b/js/src/jit-test/tests/gc/bug-1138390.js
index 887897520b60..b0310e278a20 100644
--- a/js/src/jit-test/tests/gc/bug-1138390.js
+++ b/js/src/jit-test/tests/gc/bug-1138390.js
@@ -17,12 +17,12 @@ var g = newGlobal();
 
 // Start an off thread compilation that will not run until GC has finished
 if ("gcstate" in this)
-   assertEq("mark", gcstate());
+   assertEq(gcstate(), "mark");
 g.offThreadCompileScript('23;', {});
 
 // Wait for the compilation to finish, which must finish the GC first
 assertEq(23, g.runOffThreadScript());
 if ("gcstate" in this)
-   assertEq("none", gcstate());
+   assertEq(gcstate(), "none");
 
 print("done");
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index aa53e1a889d4..ebd773ec21b4 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1714,7 +1714,7 @@ ZoneHeapThreshold::computeZoneTriggerBytes(double growthFactor, size_t lastBytes
                                            const GCSchedulingTunables &tunables)
 {
     size_t base = gckind == GC_SHRINK
-                ? lastBytes
+                ? Max(lastBytes, tunables.minEmptyChunkCount() * ChunkSize)
                 : Max(lastBytes, tunables.gcZoneAllocThresholdBase());
     double trigger = double(base) * growthFactor;
     return size_t(Min(double(tunables.gcMaxBytes()), trigger));