diff --git a/src/core.cpp b/src/core.cpp
index 8bdf0a0c..c6c95625 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -36,6 +36,7 @@ Core::Core(const ArchDef &a, Decoder &d, MemoryUnit &mem, Word id):
     w.push_back(Warp(this));
 
   w[0].activeThreads = 1;
+  w[0].spawned = true;
 }
 
 bool Core::interrupt(Word r0) {
@@ -61,7 +62,8 @@ bool Core::running() const {
 Warp::Warp(Core *c, Word id) : 
   core(c), pc(0), interruptEnable(false),
   supervisorMode(true), activeThreads(0), reg(0), pred(0),
-  shadowReg(core->a.getNRegs()), shadowPReg(core->a.getNPRegs()), id(id)
+  shadowReg(core->a.getNRegs()), shadowPReg(core->a.getNPRegs()), id(id),
+  spawned(false)
 {
   /* Build the register file. */
   Word regNum(0);
diff --git a/src/include/core.h b/src/include/core.h
index 4f4b50dc..01c16634 100644
--- a/src/include/core.h
+++ b/src/include/core.h
@@ -115,7 +115,7 @@ namespace Harp {
     std::vector<bool> shadowPReg;
 
     bool interruptEnable, shadowInterruptEnable, supervisorMode, 
-         shadowSupervisorMode;
+         shadowSupervisorMode, spawned;
 
     friend class Instruction;
   };
diff --git a/src/instruction.cpp b/src/instruction.cpp
index 2dc114af..0d6fe8d2 100644
--- a/src/instruction.cpp
+++ b/src/instruction.cpp
@@ -349,11 +349,12 @@ void Instruction::executeOn(Warp &c) {
                      D(0, "Spawning a new warp.");
                      for (unsigned i = 0; i < c.core->w.size(); ++i) {
                        Warp &newWarp(c.core->w[i]);
-                       if (newWarp.activeThreads == 0) {
+                       if (newWarp.spawned == false) {
                          newWarp.pc = reg[rsrc[0]];
                          newWarp.reg[0][rdest] = reg[rsrc[1]];
                          newWarp.activeThreads = 1;
 		         newWarp.supervisorMode = false;
+                         newWarp.spawned = true;
                          break;
                        }
                      }