diff --git a/js/src/jit-test/tests/gc/bug-1055034.js b/js/src/jit-test/tests/gc/bug-1055034.js
new file mode 100644
index 000000000000..2b2220ba104d
--- /dev/null
+++ b/js/src/jit-test/tests/gc/bug-1055034.js
@@ -0,0 +1,13 @@
+function range(n, m) {
+  var result = [];
+  for (var i = n; i < m; i++)
+    result.push(i);
+  return result;
+}
+function run(arr, func) {
+  var expected = arr["map"].apply(arr, [func]);
+  function f(m) { return arr["mapPar"].apply(arr, [func, m]); }
+    f({mode:"compile"});
+    f({mode:"seq"});
+ }
+run(range(0, 1024), function (i) { var a = []; a.length = i; });
diff --git a/js/src/jit/arm/Assembler-arm.cpp b/js/src/jit/arm/Assembler-arm.cpp
index b519dacf3b9c..bb69f42c3272 100644
--- a/js/src/jit/arm/Assembler-arm.cpp
+++ b/js/src/jit/arm/Assembler-arm.cpp
@@ -808,8 +808,14 @@ TraceOneDataRelocation(JSTracer *trc, Iter *iter, MacroAssemblerARM *masm)
     // No barrier needed since these are constants.
     gc::MarkGCThingUnbarriered(trc, &ptr, "ion-masm-ptr");
 
-    if (ptr != prior)
+    if (ptr != prior) {
         masm->ma_movPatchable(Imm32(int32_t(ptr)), dest, Assembler::Always, rs, ins);
+        // L_LDR won't cause any instructions to be updated.
+        if (rs != Assembler::L_LDR) {
+            AutoFlushICache::flush(uintptr_t(ins), 4);
+            AutoFlushICache::flush(uintptr_t(ins->next()), 4);
+        }
+    }
 }
 
 static void
diff --git a/js/src/jit/mips/Assembler-mips.cpp b/js/src/jit/mips/Assembler-mips.cpp
index 6203fb2f0bfd..da9045d5e0f0 100644
--- a/js/src/jit/mips/Assembler-mips.cpp
+++ b/js/src/jit/mips/Assembler-mips.cpp
@@ -280,17 +280,27 @@ Assembler::TraceJumpRelocations(JSTracer *trc, JitCode *code, CompactBufferReade
     }
 }
 
+static void
+TraceOneDataRelocation(JSTracer *trc, Instruction *inst)
+{
+    void *ptr = (void *)Assembler::ExtractLuiOriValue(inst, inst->next());
+    void *prior = ptr;
+
+    // No barrier needed since these are constants.
+    gc::MarkGCThingUnbarriered(trc, reinterpret_cast<void **>(&ptr), "ion-masm-ptr");
+    if (ptr != prior) {
+        Assembler::UpdateLuiOriValue(inst, inst->next(), uint32_t(ptr));
+        AutoFlushICache::flush(uintptr_t(inst), 8);
+    }
+}
+
 static void
 TraceDataRelocations(JSTracer *trc, uint8_t *buffer, CompactBufferReader &reader)
 {
     while (reader.more()) {
         size_t offset = reader.readUnsigned();
         Instruction *inst = (Instruction*)(buffer + offset);
-        void *ptr = (void *)Assembler::ExtractLuiOriValue(inst, inst->next());
-
-        // No barrier needed since these are constants.
-        gc::MarkGCThingUnbarriered(trc, reinterpret_cast<void **>(&ptr), "ion-masm-ptr");
-        Assembler::UpdateLuiOriValue(inst, inst->next(), uint32_t(ptr));
+        TraceOneDataRelocation(trc, inst);
     }
 }
 
@@ -300,12 +310,7 @@ TraceDataRelocations(JSTracer *trc, MIPSBuffer *buffer, CompactBufferReader &rea
     while (reader.more()) {
         BufferOffset bo (reader.readUnsigned());
         MIPSBuffer::AssemblerBufferInstIterator iter(bo, buffer);
-
-        void *ptr = (void *)Assembler::ExtractLuiOriValue(iter.cur(), iter.next());
-
-        // No barrier needed since these are constants.
-        gc::MarkGCThingUnbarriered(trc, reinterpret_cast<void **>(&ptr), "ion-masm-ptr");
-        Assembler::UpdateLuiOriValue(iter.cur(), iter.next(), uint32_t(ptr));
+        TraceOneDataRelocation(trc, iter.cur());
     }
 }